Cisco IOS Software SNMP Read-Write ILMI Community String
Privacy and Legal Notice
CIAC INFORMATION BULLETIN
L-052: Cisco IOS Software SNMP Read-Write ILMI Community String
February 27, 2001 18:00 GMT
PROBLEM: Cisco IOS software allows SNMP objects to be modified
without authorization by using an undocumented community string.
PLATFORM: Cisco 1400 and 1700 series.
Cisco 2600 (except that c2600-c-mz, c2600-d-mz, c2600-i-mz,
c2600-io3-mz, and c2600-ix-mz images are not vulnerable).
Catalyst 2900 ATM, 2900XL, and 2948g series.
Cisco 3620 (except that c3620-d-mz, c3620-i-mz, c3620-io3-mz,
and c3620-ix-mz images are not vulnerable).
Cisco 3640 (except that c3640-d-mz, c3640-i-mz, c3640-io3-mz,
and c3640-ix-mz images are not vulnerable).
Cisco 3660 (except that c3660-d-mz, c3660-i-mz, and c3660-ix-mz
images are not vulnerable).
Cisco MC3810 (except that mc3810-i-mz, mc3810-is-mz, mc3810-
is56i-mz, and mc3810-js-mz images are not vulnerable).
Catalyst 4232, 4840g, 5000 RSFC series switches.
Cisco 4500, 4700, and 5800 DSC series.
Cisco 6200, 6400 NRP, and 6400 NSP series.
Catalyst MSM (c6msm), 6000 Hybrid Mode (c6msfc), and 6000
Native Mode (c6sup).
Cisco RSM, 7000, 7010, 7100, 7200, ubr7200, and 7500 series.
Catalyst 8510CSR, 8510MSR, 8540CSR, and 8540MSR series.
Cisco 10000 ESR and 12000 GSR series.
LS1010 and Cisco 6260-NI2.
DistributedDirector (except that igs-w3 images are not
vulnerable).
Cisco products that are not affected by this vulnerability either
because they have no support for ATM and ILMI, or because they do
not run IOS include, but are not limited to:
Catalyst ATM blade (runs possibly affected code, but an SNMP
connection to the blade is not possible).
Cisco 800 and 805 series.
Cisco Universal Broadband Routers ubr900 and ubr920.
Cisco 1003, 1004, and 1005 series.
Cisco 1600, 2500, 2800, 4000 series.
Cisco 2500 Fixed Frad.
Cisco 3800 (not to be confused with MC3810).
Cisco 5100, 5200, and 5300 series access servers.
Catalyst 6000 Supervisor Module.
Cisco PIX Firewall.
Aironet and Cisco/Aironet wireless products.
CS11000, Cache Engine, LocalDirector, and network scaling
products (except that the Distributed Director might be
affected).
VPN products such as Altiga concentrators.
Host-based network management or access management products.
Cisco IP Telephony and telephony management software (except
those that are hosted on a vulnerable IOS platform).
Voice gateways and convergence platforms (except those that are
hosted on a vulnerable IOS platform).
Optical switch products such as the ONS 15000 series.
DAMAGE: The modification of a devices configuration may disrupt
normal operations of the device resulting in a denial of service
(DoS).
SOLUTION: Cisco is providing free upgrades to affected users and has
a suggested workaround for certain IOS releases. Use the
information provided in the bulletin to determine if your system
has the defective software.
VULNERABILITY The risk is LOW. A malicious party would have to know the
ASSESSMENT: undocumented community name.
[****** Begin Cisco Bulletin ******]
Cisco Security Advisory:
Cisco IOS Software SNMP Read-Write ILMI Community String Vulnerability
Revision 1.0: INTERIM
For Public Release 2001 February 27 04:00 US/Eastern (UTC+0500)
_______________________________________________________________
Summary
Cisco IOS software releases based on versions 11.x and 12.0 contain
a defect that allows a limited number of SNMP objects to be viewed
and modified without authorization using a undocumented ILMI
community string. Some of the modifiable objects are confined to the
MIB-II system group, such as "sysContact", "sysLocation", and
"sysName", that do not affect the device's normal operation but that
may cause confusion if modified unexpectedly. The remaining objects
are contained in the LAN-EMULATION-CLIENT and PNNI MIBs, and
modification of those objects may affect ATM configuration. An
affected device might be vulnerable to a denial-of-service attack if
it is not protected against unauthorized use of the ILMI community
string.
The vulnerability is only present in certain combinations of IOS
releases on Cisco routers and switches. ILMI is a necessary
component for ATM, and the vulnerability is present in every IOS
release that contains the supporting software for ATM and ILMI
without regard to the actual presence of an ATM interface or the
physical ability of the device to support an ATM connection.
To remove this vulnerability, Cisco is offering free software
upgrades for all affected platforms. The defect is documented in
DDTS record CSCdp11863.
In lieu of a software upgrade, a workaround can be applied to
certain IOS releases by disabling the ILMI community or "*ilmi" view
and applying an access list to prevent unauthorized access to SNMP.
Any affected system, regardless of software release, may be
protected by filtering SNMP traffic at a network perimeter or on
individual devices.
This notice will be posted at
http://www.cisco.com/warp/public/707/ios-snmp-ilmi-vuln-pub.shtml.
Affected Products
The vulnerability is present only in certain releases of Cisco IOS
Software versions 11.x and 12.0 for router and switch products that
include support for Asynchronous Transfer Mode (ATM) networking and
Interim Local Management Interface (ILMI), and it is present without
regard to any physical capability for supporting an ATM interface.
Cisco IOS Software versions based on 10.3 and earlier do not contain
the vulnerability. The defect was introduced in 11.0(0.2). All Cisco
IOS software releases of 12.1 and later have been repaired and are
not vulnerable to the defect described in this advisory.
To determine the software running on a Cisco product, log in to the
device and issue the command "show version" to display the system
banner. Cisco IOS software will identify itself as "Internetwork
Operating System Software" or simply "IOS (tm)". The image name will
be displayed between parentheses, usually on the next line of
output, followed by "Version" and the IOS release name. Other Cisco
devices will not have the "show version" command or will give
different output.
The following example identifies a Cisco product running IOS release
12.0(3) with an installed image name of C2500-IS-L:
Cisco Internetwork Operating System Software IOS (tm)
2500 Software (C2500-IS-L), Version 12.0(3), RELEASE SOFTWARE
The device is not vulnerable to the defect described in this
advisory since the model 2500 router is specifically excluded in the
list of unaffected products shown below.
Cisco devices that may be running an affected IOS software release
include, but are not limited to:
* Cisco 1400 and 1700 series.
* Cisco 2600 (except that c2600-c-mz, c2600-d-mz, c2600-i-mz,
c2600-io3-mz, and c2600-ix-mz images are not vulnerable).
* Catalyst 2900 ATM, 2900XL, and 2948g series.
* Cisco 3620 (except that c3620-d-mz, c3620-i-mz, c3620-io3-mz,
and c3620-ix-mz images are not vulnerable).
* Cisco 3640 (except that c3640-d-mz, c3640-i-mz, c3640-io3-mz,
and c3640-ix-mz images are not vulnerable).
* Cisco 3660 (except that c3660-d-mz, c3660-i-mz, and c3660-ix-mz
images are not vulnerable).
* Cisco MC3810 (except that mc3810-i-mz, mc3810-is-mz,
mc3810-is56i-mz, and mc3810-js-mz images are not vulnerable).
* Catalyst 4232, 4840g, 5000 RSFC series switches.
* Cisco 4500, 4700, and 5800 DSC series.
* Cisco 6200, 6400 NRP, and 6400 NSP series.
* Catalyst MSM (c6msm), 6000 Hybrid Mode (c6msfc), and 6000 Native
Mode (c6sup).
* Cisco RSM, 7000, 7010, 7100, 7200, ubr7200, and 7500 series.
* Catalyst 8510CSR, 8510MSR, 8540CSR, and 8540MSR series.
* Cisco 10000 ESR and 12000 GSR series.
* LS1010 and Cisco 6260-NI2.
* DistributedDirector (except that igs-w3 images are not
vulnerable).
Cisco products that are not affected by this vulnerability either
because they have no support for ATM and ILMI, or because they do
not run IOS include, but are not limited to:
* Catalyst ATM blade (runs possibly affected code, but an SNMP
connection to the blade is not possible).
* Cisco 800 and 805 series.
* Cisco Universal Broadband Routers ubr900 and ubr920.
* Cisco 1003, 1004, and 1005 series.
* Cisco 1600, 2500, 2800, 4000 series.
* Cisco 2500 Fixed Frad.
* Cisco 3800 (not to be confused with MC3810).
* Cisco 5100, 5200, and 5300 series access servers.
* Catalyst 6000 Supervisor Module.
* Cisco PIX Firewall.
* Aironet and Cisco/Aironet wireless products.
* CS11000, Cache Engine, LocalDirector, and network scaling
products (except that the Distributed Director might be
affected).
* VPN products such as Altiga concentrators.
* Host-based network management or access management products.
* Cisco IP Telephony and telephony management software (except
those that are hosted on a vulnerable IOS platform).
* Voice gateways and convergence platforms (except those that are
hosted on a vulnerable IOS platform).
* Optical switch products such as the ONS 15000 series.
Details
ILMI (Interim Local Management Interface) is an independent industry
standard used for configuration of ATM (Asynchronous Transfer Mode)
interfaces. The standard specifies the use of mechanisms and formats
previously defined by SNMP (Simple Network Management Protocol).
Although it is based on SNMP, ILMI communication actually occurs
using a transport other than IP (Internet Protocol) that traverses
only the physical ATM link. ILMI is essential to functions such as
ATM auto-discovery and LANE (LAN Emulation).
SNMP "objects" are variables that are organized into a MIB
(Management Information Base). The MIB has a tree structure and
contains both operational (read-only) data as well as configuration
(read-write) options. By specifying a community string of "ILMI" in
an SNMP request, access can be obtained to read the objects in three
specific parts of the overall management tree structure on any
device affected by this vulnerability: the MIB-II system group, the
LAN-EMULATION-CLIENT MIB, and the PNNI (Private Network-to-Network
Interface) MIB. A subset of objects in each part can be modified
using the same "ILMI" community string.
The MIB-II system group contains basic information about the device
itself. The number of objects that can be modified is limited.
Examples include:
* system.sysContact: The contact information for the person or
organization responsible for managing the device.
* system.sysLocation: A description of the physical location where
the device is installed or operating.
* system.sysName: The hostname of the device, how it identifies
itself at the console prompt. (This might not be the same name
by which the device is known to other hosts on the network.)
Most of the objects in the system MIB are read-only and cannot be
changed via SNMP, such as the time elapsed since the previous
restart and textual descriptions of the device's hardware and
software.
Numerous objects can be viewed in the LAN-EMULATION-CLIENT MIB and
PNNI MIB, and modification of some of the read-write objects can
have an affect on ATM operation of the device. The objects in the
LAN-EMULATION-CLIENT MIB can only be viewed or modified if LANE has
already been configured on the device.
Access to SNMP in Cisco IOS software can be limited by applying
access control lists (ACLs), by modifying or removing the SNMP view,
by removing the community string from the running configuration, or
by disabling the SNMP service. Any SNMP query that does not meet the
criteria for access is promptly discarded when such protective
measures are in place. If a query does meet the criteria for access,
then a response is formulated and sent.
It is possible to configure the device so that the ILMI community
string is unavailable in all IOS 11.1 and higher releases. The
particular method selected to accomplish this depends on the
specific IOS release and configuration.
This defect is documented as CSCdp11863. The vulnerability is
repaired by imposing a test such that an SNMP request using the
"ILMI" community string will only be recognized if it has been
transported by ILMI.
ATM functionality was added in various 10.x releases of Cisco IOS
software. However, the function containing the defect was introduced
when support for ILMI and other ATM features was added in IOS
release 11.0(0.2). Therefore, all prior releases are not vulnerable.
Impact
If SNMP requests can be received by an affected device, then certain
MIB objects can be viewed without proper authorization, causing a
violation of confidentiality.
A subset of the readable MIB objects can be modified without
authorization to cause a failure of integrity. For example, the
hostname can be modified so as to confuse network adminstrators, or
the contact and location information could be changed with a goal of
disrupting operations or embarassing whoever is responsible for the
device.
Objects in the LAN-EMULATION-CLIENT and PNNI MIBs can be viewed and
modified, thus resulting in changes to the operation of ATM
functions. If ATM is in use on the device, this may result in a
failure of availability.
Any affected device that is not otherwise protected against the
receipt of SNMP packets is vulnerable to a denial-of-service (DoS)
attack by flooding the SNMP port with read or write requests.
Software Versions and Fixes
The following table summarizes the known affected Cisco IOS software
releases and the earliest estimated dates of availability for fixed
releases. All dates are tentative and subject to change.
Each row of the table describes a release train and the platforms or
products for which it is intended. If a given release train is
vulnerable, then the earliest possible releases that contain the fix
and the anticipated date of availability for each are listed in the
"Rebuild", "Interim", and "Maintenance" columns. If a device is
running an earlier release that is known to be vulnerable, it should
be upgraded to at least the indicated version.
When selecting a release, keep in mind the following definitions:
Maintenance
Most heavily tested and highly recommended release of any
label in a given row of the table.
Rebuild
Constructed from the previous maintenance or major release in
the same train, it contains the fix for a specific defect.
Although it receives less testing, it contains only the
minimal changes necessary to effect the repair.
Interim
Built at regular intervals between maintenance releases and
receive less testing. Interims should be selected only if
there is no other suitable release that addresses the
vulnerability. Interim releases are usually not available for
customer download via CCO without prior arrangement.
In all cases, customers should exercise caution to be certain the
devices to be upgraded contain sufficient memory and that current
hardware and software configurations will continue to be supported
properly by the new release. If the information is not clear,
contact the Cisco TAC for assistance as shown in the following
section.
More information on IOS release names and abbreviations is available
at http://www.cisco.com/warp/public/620/1.html.
+===========================================================================+
| Train | Description of | Availability of Fixed Releases* |
| | Image or Platform | |
+===========================================================================+
| 10.3-based Releases and | | | |
| Earlier | Rebuild | Interim** | Maintenance |
+===========================================================================+
| 10.3 and | | |
| earlier |All |Not affected |
+===========================================================================+
| 11.0-based Releases | Rebuild | Interim** | Maintenance |
+===========================================================================+
| | |11.0(22a) | | |
| 11.0 |Major GD release | | | |
| |for all platforms |2001-Mar-05 | | |
+===========================================================================+
| 11.1-based Releases | Rebuild | Interim** | Maintenance |
+===========================================================================+
| | |11.1(24a) | | |
| 11.1 |Major release for | | | |
| |all platforms |2001-Mar-05 | | |
+----------+-------------------+------------+---------------+---------------+
| |ED release for | | |12.1(7) |
| 11.1AA |access servers: | | | |
| |1600, 3200, and | | | |
| |5200 series. | | |2001-Feb-26 |
+----------+-------------------+------------+---------------+---------------+
| |Platform-specific |11.1(36)CA1 | | |
| 11.1CA |support for 7500, | | | |
| |7200, 7000, and RSP|2001-Mar-02 | | |
+----------+-------------------+------------+---------------+---------------+
| |ISP train: added | | | |
| |support for FIB, |11.1(36)CC1 | | |
| 11.1CC |CEF, and NetFlow on| | | |
| |7500, 7200, 7000, |2001-Mar-02 | | |
| |and RSP | | | |
+----------+-------------------+------------+---------------+---------------+
| |Added support for |12.0(11)ST2 | | |
| 11.1CT |Tag Switching on | | | |
| |7500, 7200, 7000, | | | |
| |and RSP |2001-Feb-26 | | |
+----------+-------------------+------------+---------------+---------------+
| | |11.1(28)IA1 | | |
| 11.1IA |DistributedDirector| | | |
| |only |2001-Feb-26 | | |
+===========================================================================+
| 11.2-based Releases | Rebuild | Interim** | Maintenance |
+===========================================================================+
| | |11.2(25a) | | |
| 11.2 |Major release, | | | |
| |general deployment |2001-Mar-05 | | |
+----------+-------------------+------------+---------------+---------------+
| |Platform-specific | | | |
| |support for IBM | | |12.1(7) |
| 11.2BC |networking, CIP, | | | |
| |and TN3270 on 7500,| | |2001-Feb-26 |
| |7000, and RSP | | | |
+----------+-------------------+------------+---------------+---------------+
| |Early deployment |12.0(15)S1 | | |
| 11.2GS |release to support | | | |
| |12000 GSR |2001-Feb-20 | | |
+----------+-------------------+------------+---------------+---------------+
| | |11.2(25a)P | | |
| 11.2P |New platform | | | |
| |support |2001-Mar-05 | | |
+----------+-------------------+------------+---------------+---------------+
| | | | |12.1WC |
| 11.2SA |Catalyst 2900XL | | | |
| |switch only | | |2001-Apr-12 |
+----------+-------------------+------------+---------------+---------------+
| | | | |12.0(10)W5(18c)|
| 11.2WA3 |LS1010 ATM switch | | | |
| | | | |Available |
+----------+-------------------+------------+---------------+---------------+
| | |11.2(25a)P | | |
|11.2(4)XA |Initial release for| | | |
| |the 1600 and 3600 |2001-Mar-05 | | |
+----------+-------------------+------------+---------------+---------------+
| |Initial release for| | | |
| |the 5300 and |11.2(9)XA1 | | |
|11.2(9)XA |digital modem | | | |
| |support for the |Unscheduled | | |
| |3600 | | | |
+===========================================================================+
| 11.3-based Releases | Rebuild | Interim** | Maintenance |
+===========================================================================+
| | |11.3(11b) | | |
| 11.3 |Major release for | | | |
| |all platforms |2001-Mar-05 | | |
+----------+-------------------+------------+---------------+---------------+
| |ED for dial | | | |
| |platforms and |11.3(11a)AA | | |
| 11.3AA |access servers: | | | |
| |5800, 5200, 5300, |2001-Mar-05 | | |
| |7200 | | | |
+----------+-------------------+------------+---------------+---------------+
| |Early deployment |12.1(5)DA1 | | |
| 11.3DA |train for ISP DSLAM| | | |
| |6200 platform |2001-Feb-28 | | |
+----------+-------------------+------------+---------------+---------------+
| |Early deployment | | | |
| |train for |12.1(4)DB1 | | |
| |ISP/Telco/PTT xDSL | | | |
| 11.3DB |broadband | | | |
| |concentrator | | | |
| |platform, (NRP) for|2001-Feb-26 | | |
| |6400 | | | |
+----------+-------------------+------------+---------------+---------------+
| |Short-lived ED | |
| 11.3HA |release for ISR |Not Vulnerable |
| |3300 (SONET/SDH | |
| |router) | |
+----------+-------------------+------------+---------------+---------------+
| | |11.3(1)MA8 | | |
| 11.3MA |MC3810 | | | |
| |functionality only |Unscheduled | | |
+----------+-------------------+------------+---------------+---------------+
| |Voice over IP, |12.1(7) | | |
| 11.3NA |media convergence, | | | |
| |various platforms |2001-Mar-05 | | |
+----------+-------------------+------------+---------------+---------------+
| |Early deployment |11.3(11b)T1 | | |
| 11.3T |major release, | | | |
| |feature-rich for | | | |
| |early adopters |2001-Mar-05 | | |
+----------+-------------------+------------+---------------+---------------+
| |Multilayer | | | |
| |Switching and | | |12.0(14)W5(20) |
| |Multiprotocol over | | | |
| 11.3WA4 |ATM functionality | | | |
| |for Catalyst 5000 | | | |
| |RSM, 4500, 4700, | | |2001-Feb-28 |
| |7200, 7500, LS1010 | | | |
+----------+-------------------+------------+---------------+---------------+
| | |11.3(11b)T1 | | |
|11.3(2)XA |Introduction of | | | |
| |ubr7246 and 2600 |2001-Mar-05 | | |
+===========================================================================+
| 12.0-based Releases | Rebuild | Interim** | Maintenance |
+===========================================================================+
| |General deployment | |12.0(7.1) |12.0(16) |
| 12.0 |release for all | | | |
| |platforms | |Available |2001-Feb-20 |
+----------+-------------------+------------+---------------+---------------+
| | | |12.0(7.1)T | |
| 12.0DA |xDSL support: 6100,| | | |
| |6200 | |Available | |
+----------+-------------------+------------+---------------+---------------+
| |ISP/Telco/PTT xDSL |12.1(4)DB1 | | |
| 12.0DB |broadband | | | |
| |concentrator | | | |
| |platforms |2001-Feb-26 | | |
+----------+-------------------+------------+---------------+---------------+
| | |12.1(4)DC2 | | |
| 12.0DC |6400 Access | | | |
| |Concentrator |2001-Feb-26 | | |
+----------+-------------------+------------+---------------+---------------+
| | |12.0(15)S1 | | |
| 12.0S |Core/ISP support: | | | |
| |GSR, RSP, c7200 |2001-Feb-20 | | |
+----------+-------------------+------------+---------------+---------------+
| | |12.0(15)SC1 | | |
| 12.0SC |Cable/broadband | | | |
| |ISP: ubr7200 |2001-Feb-26 | | |
+----------+-------------------+------------+---------------+---------------+
| | |12.0(14)SL1 | | |
| 12.0SL |10000 ESR: c10k | | | |
| | |2001-Feb-26 | | |
+----------+-------------------+------------+---------------+---------------+
| |General deployment |12.0(11)ST2 | | |
| 12.0ST |release for all | | | |
| |platforms |2001-Feb-26 | | |
+----------+-------------------+------------+---------------+---------------+
| | |12.1(5c)E8 | | |
| 12.0SX |Early Deployment | | | |
| |(ED) |2001-Feb-26 | | |
+----------+-------------------+------------+---------------+---------------+
| |Early | | | |
| |Deployment(ED): | | |12.1(7) |
| 12.0T |VPN, Distributed | | | |
| |Director, various | | |2001-Feb-26 |
| |platforms | | | |
+----------+-------------------+------------+---------------+---------------+
| |cat8510c, cat8540c,| | | |
| |ls1010, cat8510m, | |12.0(10)W5(18c)|12.0(14)W5(20) |
| |cat8540m, c5atm, | | | |
| |c5atm, c3620, | | | |
| |c3640, c4500, | | | |
| 12.0W5 |c5rsfc, c5rsm, | |Available |2001-Feb-28 |
| |c7200, rsp, | | | |
| |cat2948g, cat4232 | | | |
| +-------------------+------------+---------------+---------------+
| | | |12.0(10)W5(18d)|12.0(14)W5(20) |
| |c6msm | | | |
| | | |Available |2001-Feb-28 |
+----------+-------------------+------------+---------------+---------------+
| |General deployment | | |12.0(13)WT6(1) |
| 12.0WT |release for all | | | |
| |platforms | | |2001-Feb-20 |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment | | |12.1(7) |
| 12.0XA |(ED): limited | | | |
| |platforms | | |2001-Feb-26 |
+----------+-------------------+------------+---------------+---------------+
| | | | |12.1(7) |
| 12.0XB |Short-lived early | | | |
| |deployment release | | |2001-Feb-26 |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment | | |12.1(7) |
| 12.0XC |(ED): limited | | | |
| |platforms | | |2001-Feb-26 |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment | | |12.1(7) |
| 12.0XD |(ED): limited | | | |
| |platforms | | |2001-Feb-26 |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment |12.1(5c)E8 | | |
| 12.0XE |(ED): limited | | | |
| |platforms |2001-Feb-26 | | |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment | | |12.1(7) |
| 12.0XF |(ED): limited | | | |
| |platforms | | |2001-Feb-26 |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment | | |12.1(7) |
| 12.0XG |(ED): limited | | | |
| |platforms | | |2001-Feb-26 |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment |12.0(4)XH5 | | |
| 12.0XH |(ED): limited | | | |
| |platforms |2001-Mar-05 | | |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment | | |12.1(7) |
| 12.0XI |(ED): limited | | | |
| |platforms | | |2001-Feb-26 |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment | | |12.1(7) |
| 12.0XJ |(ED): limited | | | |
| |platforms | | |2001-Feb-26 |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment |12.0(7)XK4 | | |
| 12.0XK |(ED): limited | | | |
| |platforms |Unscheduled | | |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment |12.0(4)XH5 | | |
| 12.0XL |(ED): limited | | | |
| |platforms |2001-Mar-05 | | |
+----------+-------------------+------------+---------------+---------------+
| | | | |12.1(7) |
| 12.0XM |Short-lived early | | | |
| |deployment release | | |2001-Feb-26 |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment | | | |
| 12.0XN |(ED): limited | | | |
| |platforms | | | |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment | | |12.1WC |
| 12.0XP |(ED): limited | | | |
| |platforms | | |2001-Apr-12 |
+----------+-------------------+------------+---------------+---------------+
| | | | |12.1(7) |
| 12.0XQ |Short-lived early | | | |
| |deployment release | | |2001-Feb-26 |
+----------+-------------------+------------+---------------+---------------+
| | |12.1(5)T5 | | |
| 12.0XR |Short-lived early | | | |
| |deployment release |2001-Mar-05 | | |
+----------+-------------------+------------+---------------+---------------+
| | |12.1(5c)E8 | | |
| 12.0XS |Short-lived early | | | |
| |deployment release |2001-Feb-26 | | |
+----------+-------------------+------------+---------------+---------------+
| |Early Deployment | | |12.1WC |
| 12.0XU |(ED): limited | | | |
| |platforms | | |2001-Apr-12 |
+----------+-------------------+------------+---------------+---------------+
| | |12.1(5)T5 | | |
| 12.0XV |Short-lived early | | | |
| |deployment release |2001-Mar-05 | | |
+===========================================================================+
|12.1-based and Later Releases | Rebuild | Interim** | Maintenance |
+===========================================================================+
| All 12.1 | | |
| Releases |Various platforms |Not Vulnerable |
+===========================================================================+
| Notes |
+===========================================================================+
| * All dates are estimated and Subject to change. |
| |
|** Interim releases are subjected to less rigorous testing than regular |
| maintenance releases, and may have serious bugs. |
+===========================================================================+
Obtaining Fixed Software
Cisco is offering free software upgrades to remedy this
vulnerability for all affected customers. Customers with service
contracts may upgrade to any software release. Customers without
contracts may upgrade only within a single row of the table above,
except that any available fixed software release will be provided to
any customer who can use it and for whom the standard fixed software
release is not yet available. Customers may install only the feature
sets they have purchased.
Note that not all fixed software may be available as of the release
date of this notice.
Customers with contracts should obtain upgraded software through
their regular update channels. For most customers, this means that
upgrades should be obtained via Cisco's Software Center at
http://www.cisco.com/.
Customers without contracts or warranty should get their upgrades by
contacting the Cisco Technical Assistance Center (TAC) as shown
below:
* (800) 553-2447 (toll-free in North America)
* +1 408 526 7209 (toll call from anywhere in the world)
* e-mail: tac@cisco.com
See http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for
additional TAC contact information, including instructions and
e-mail addresses for use in various languages.
Give the URL of this notice as evidence of your entitlement to a
free upgrade. Free upgrades for non-contract customers must be
requested through the TAC. Please do not contact either
"psirt@cisco.com" or "="security-alert@cisco.com " for software
upgrades; faster results will be obtained by contacting the TAC
directly.
Workarounds
Several workarounds are available based on customer needs,
equipment, and software features. The usefulness and practicality of
each workaround depends on the IOS release running on the device and
many variables in the customer's environment. Customers are urged to
consider each of the following alternatives carefully before
deploying. These workarounds are only needed if it is not possible
to upgrade to an unaffected release of IOS software.
A. Default workaround for use with releases for which no other
workarounds are effective:
1. Applying access lists to all the interfaces of the
vulnerable device blocking SNMP from all hosts but those
authorized to manage the devices.
2. Blocking SNMP access at the edge of the network to prevent
undesirable SNMP traffic from entering the network
containing the vulnerable device.
Access lists should be deployed with careful consideration of
the possible effects on network operation and performance. Also
note that authentication based on an IP source address is weak,
so the preceding method will not protect against certain types
of attacks in which the IP source address has been spoofed.
Further information can be found in the Cisco document
"Improving Security on Cisco Routers", available at
http://www.cisco.com/warp/public/707/21.html
B. For affected releases based on IOS 11.1:
1. Remove the view so that the ILMI community cannot be
reached:
no snmp-server view *ilmi
2. This configuration will not survive a system reload. The
command must be re-entered after every restart of the
system.
C. For affected releases of IOS 11.2 through 11.3(8) NOT REQUIRING
ATM:
In this affected range of releases, the ILMI community string
can be modified or deleted. However, the changes will not
persist through a reboot of the device. These instructions must
be re-applied following every system reload of the affected
device:
1. Expose the undocumented ILMI community string so it can be
modified:
snmp-server community ILMI RW
The preceding command may cause an error that can be safely
ignored.
2. Disable read-write capability for the same community:
no snmp-server community ILMI RW
If an error is displayed, then this workaround cannot be
applied to the device. Use the default workarounds
presented in the first item above.
3. Since this configuration will not survive a system reload,
the command must be re-entered after every restart of the
system.
If the command in item 2 above did not generate an error and ATM
is not needed on this device, then this workaround is complete.
D. For affected releases of IOS 11.2 through 11.3(8) THAT REQUIRE
ATM:
This workaround will allow ILMI to continue to function for ATM
while constraining who may reconfigure the device by way of the
ILMI community string:
1. Create a simple ACL to deny access using the following
command. If "66" is already in use, choose a different
two-digit number:
access-list 66 deny any
2. Apply it generally to the ILMI community to restrict its
view:
snmp community ILMI view *ilmi RW 66
An error will be reported if the *ilmi view doesn't exist.
If that occurs, then use the following command to
explicitly restrict the ILMI view:
snmp community ILMI RW 66
If the preceding command produces persistent errors, then
this workaround cannot be applied to this device. Use the
default workarounds presented in the first item above.
E. For affected releases of IOS 11.3(9) through 12.0(2)T NOT
REQUIRING ATM:
All versions of IOS in this range will accept this workaround,
and the change will remain in place after a system reload.
1. Expose the undocumented ILMI community string so it can be
modified:
snmp-server community ILMI RW
The preceding command may cause an error that can be safely
ignored.
2. Disable read-write capability for the same community:
no snmp-server community ILMI RW
If an error is displayed, then this workaround cannot be
applied to the device. Stop this procedure and use the
default workarounds presented in the first item above.
F. For affected releases of IOS 11.3(9) through 12.0(2)T THAT
REQUIRE ATM:
This workaround will allow ILMI to continue to function for ATM
while constraining who may reconfigure the device by way of the
ILMI community string:
1. Create a simple ACL to deny access using the following
command. If "66" is already in use, choose a different
two-digit number:
access-list 66 deny any
2. Apply it generally to the ILMI community to restrict its
view:
snmp community ILMI view *ilmi RW 66
An error will be reported if the *ilmi view doesn't exist.
If that occurs, then use the following command to
explicitly restrict the ILMI view:
snmp community ILMI RW 66
If the preceding command produces persistent errors, then
this workaround cannot be applied to this device. Use the
default workaround presented in the first item above.
G. For affected releases of IOS 12.0(3)T and later:
These releases of IOS include support for Simple Network
Management Protocol version 3 (SNMPv3), which is required for
this workaround.
1. Confirm the presence of SNMPv3 support by asking the
console CLI (command-line interpreter) for assistance with
options to complete the snmp-server command. Enter config
mode, enter the command shown below, and note the expected
response:
snmp-server user test test ?
remote Specify a remote SNMP entity to which the user belongs
v1 user using the v1 security model
v2c user using the v2c security model
v3 user using the v3 security model
If the preceding command did not produce the expected
results, then SNMPv3 is not supported in the release and
this workaround cannot be applied. Stop this procedure and
consider applying the default workaround presented above in
the first item.
Otherwise, if the device responded as expected, continue
with the following explanation and instructions.
In these IOS releases (12.0(3)T and later), ILMI packets are
processed by the SNMP engine in the same manner as ordinary IP
SNMP packets. An access control list or a view applied to the
ILMI community string will be processed whether the transport is
ILMI or IP. However, the only types of access control lists that
can be applied to a community string are via IP access-list
statements, which when applied, block ALL non-IP packets,
including ILMI packets. Modifying or deleting the *ilmi view
will also affect the packets transported by ILMI, so workarounds
that change the view are equally ineffective at permitting ILMI
while denying SNMP. In this range of releases, it is not
possible to apply a workaround that denies IP SNMP packets that
does not also deny ILMI SNMP packets.
H. For affected releases of IOS 12.0(3)T and later NOT REQUIRING
ATM:
1. Expose the undocumented ILMI community string so it can be
modified:
snmp-server community ILMI RW
The preceding command may cause an error that can be safely
ignored.
2. Disable read-write capability for the same community:
no snmp-server community ILMI RW
If an error is displayed, then this workaround cannot be
applied to the device. Stop this procedure and consider
using the default workaround.
I. For affected releases of IOS 12.0(3)T and later THAT REQUIRE
ATM:
NOTE: This section also applies to 12.0-based ATM switch
software such as for the LS1010 and the 8500 series.
The only effective workaround for systems in this category is
the default workaround:
1. Applying access lists to all the interfaces of the
vulnerable device blocking SNMP from all hosts but those
authorized to manage the devices.
2. Blocking SNMP access at the edge of the network to prevent
undesirable SNMP traffic from entering the network
containing the vulnerable device.
Access lists should be deployed with careful consideration of
the possible effects on network operation and performance. Also
note that authentication based on an IP source address is weak,
so the preceding method will not protect against certain types
of attacks in which the IP source address has been spoofed.
In this range of releases it is not possible to block IP SNMP
packets while permitting ILMI SNMP packets. The alternative
workarounds presented previously will almost certainly cause a
failure of ATM ILMI communications resulting in a loss of ATM
connectivity, either immediately upon configuration, or
unexpectedly at some later time. Either use the default
workaround or upgrade to fixed software.
Exploitation and Public Announcements
This vulnerability is known to the engineering staff of several
Cisco customers. Cisco considers it known to the public prior to the
publication of this notice.
Cisco is aware of one recent incident involving the unauthorized
modification of a router that appears to have resulted from this
vulnerability. However, it may have been the unintended side-effect
of a test of the vulnerability.
Cisco is not aware of any available tools specifically designed to
make use of this vulnerability. However, various off-the-shelf
network management programs could easily be used to test for this
vulnerability and to exploit it. Certain widely-available programs
known to the cracker community could be modified by any reasonably
competent programmer to automate the abuse of this vulnerability.
Cisco is not aware of any general public discussion of this
vulnerability other than the exceptions previously noted.
Status of This Notice: INTERIM
This is an interim security advisory. Cisco anticipates issuing
updated versions of this notice at irregular intervals as there are
material changes in the facts, and will continue to update this
notice as necessary. The reader is warned that this notice may
contain inaccurate or incomplete information. Although Cisco cannot
guarantee the accuracy of all statements in this notice, all of the
facts have been checked to the best of our ability. Cisco
anticipates issuing monthly updates of this notice until it reaches
FINAL status.
A standalone copy or paraphrase of the text of this security
advisory that omits the distribution URL in the following section is
an uncontrolled copy, and may lack important information or contain
factual errors.
Distribution
This notice will be posted at
http://www.cisco.com/warp/public/707/ios-snmp-ilmi-vuln-pub.shtml .
In addition to Worldwide Web posting, a text version of this notice
will be clear-signed with the Cisco PSIRT PGP key and will be posted
to the following e-mail and Usenet news recipients:
* cust-security-announce@cisco.com
* bugtraq@securityfocus.com
* firewalls@lists.gnac.com
* first-teams@first.org (including CERT/CC
* cisco@spot.colorado.edu
* cisco-nsp@puck.nether.net
* comp.dcom.sys.cisco
* Various internal Cisco mailing lists
Future updates of this notice, if any, will be placed on Cisco's
Worldwide Web server, but may or may not be actively announced on
mailing lists or newsgroups. Users concerned about this problem are
encouraged to check the URL given above for any updates.
Revision History
Revision 1.0 2001-Feb-27 First interim public version
Cisco Product Security Incident Procedures
Instructions for reporting product security vulnerabilities in Cisco
products, obtaining assistance with customer security incidents, and
registering to receive security information from Cisco can be found
at http://www.cisco.com/warp/public/707/sec_incident_response.shtml
, including instructions for press inquiries regarding Cisco
Security Advisories.
_______________________________________________________________
Copyright 2001 by Cisco Systems, Inc. This notice may be
redistributed freely after the release date given at the top of the
text, provided that redistributed copies are complete and
unmodified, and include all date and version information.
[****** End Cisco Bulletin ******]
CIAC wishes to acknowledge the contributions of Cisco Systems Inc. for the
information contained in this bulletin.
CIAC services are available to DOE, DOE Contractors, and the NIH. CIAC
can be contacted at:
Voice: +1 925-422-8193 (7 x 24)
FAX: +1 925-423-8002
STU-III: +1 925-423-2604
E-mail: ciac@llnl.gov
World Wide Web: http://www.ciac.org/
http://ciac.llnl.gov
(same machine -- either one will work)
Anonymous FTP: ftp.ciac.org
ciac.llnl.gov
(same machine -- either one will work)
This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial products,
process, or service by trade name, trademark, manufacturer, or
otherwise, does not necessarily constitute or imply its endorsement,
recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
advertising or product endorsement purposes.
UCRL-MI-119788
[Privacy and Legal Notice]
TUCoPS is optimized to look best in Firefox® on a widescreen monitor (1440x900 or better).
Site design & layout copyright © 1986-2024 AOH
