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Cisco Security Advisory: Remote Access VPN and SIP Vulnerabilities in
Cisco PIX and Cisco ASA
Advisory ID: cisco-sa-20080903-asa
Revision 1.0
For Public Release 2008 September 3 1600 UTC (GMT)
+---------------------------------------------------------------------
Summary
======
Multiple vulnerabilities exist in the Cisco ASA 5500 Series Adaptive
Security Appliances and Cisco PIX Security Appliances that may result
in a reload of the device or disclosure of confidential information.
This security advisory outlines details of the following
vulnerabilities:
* Erroneous SIP Processing Vulnerabilities
* IPSec Client Authentication Processing Vulnerability
* SSL VPN Memory Leak Vulnerability
* URI Processing Error Vulnerability in SSL VPNs
* Potential Information Disclosure in Clientless VPNs
Note: These vulnerabilities are independent of each other. A device
may be affected by one vulnerability and not affected by another.
Cisco has released free software updates that address these
vulnerabilities. Workarounds that mitigate some of these
vulnerabilities are available.
This advisory is posted at:
http://www.cisco.com/warp/public/707/cisco-sa-20080903-asa.shtml
Affected Products
================
The following paragraphs describe the affected Cisco ASA and Cisco
PIX software versions:
Vulnerable Products
+------------------
The following sections provide details on the versions of Cisco ASA
that are affected by each vulnerability.
The show version command-line interface (CLI) command can be used to
determine if a vulnerable version of the Cisco PIX or Cisco ASA
software is running. The following example shows a Cisco ASA device
that runs software release 8.0(2):
ASA# show version
Cisco Adaptive Security Appliance Software Version 8.0(2)
Device Manager Version 6.0(1)
[...]
Customers who use the Cisco Adaptive Security Device Manager (ASDM)
to manage their devices can find their software version displayed in
a table in the login window or in the upper left corner of the ASDM
window.
Erroneous SIP Processing Vulnerabilities
Cisco PIX and Cisco ASA devices configured for SIP inspection are
vulnerable to multiple processing errors that may result in denial of
service attacks. Cisco PIX and ASA software versions prior to 7.0(7)
16, 7.1(2)71, 7.2(4)7, 8.0(3)20, and 8.1(1)8 are vulnerable to these
SIP processing errors.
IPSec Client Authentication Processing Vulnerability
Cisco PIX and Cisco ASA devices that terminate remote access VPN
connections are vulnerable to a denial of service attack if the
device is running software versions prior to 7.2(4)2, 8.0(3)14, and
8.1(1)4. Cisco PIX and Cisco ASA devices that run software versions
7.0 and 7.1 are not affected by this vulnerability.
SSL VPN Memory Leak Vulnerability
Cisco ASA devices that terminate clientless remote access VPN
connections are vulnerable to a denial of service attack affecting
the SSL processing software if the device is running a software
version prior to 7.2(4)2, 8.0(3)14, or 8.1(1)4. Cisco ASA devices
that run software versions 7.0 and 7.1 are not affected by this
vulnerability.
URI Processing Error Vulnerability in SSL VPNs
Cisco ASA devices that terminate clientless remote access VPN
connections are vulnerable to a denial of service attack in the HTTP
server if the device is running software versions prior to 8.0(3)15,
and 8.1(1)5. Cisco ASA devices that run software versions 7.0, 7.1,
or 7.2 are not affected by this vulnerability.
Potential Information Disclosure in Clientless VPNs
Cisco ASA devices that terminate clientless remote access VPN
connections are vulnerable to potential information disclosure if the
device is running affected 8.0 or 8.1 software versions. Cisco ASA
devices running software versions 7.0, 7.1, or 7.2 are not affected
by this vulnerability. Cisco ASA devices the run software versions
prior to 8.0(3)15 and 8.1(1)4, or after 8.0(3)16 and 8.1(1)5 are also
not affected by this vulnerability.
Products Confirmed Not Vulnerable
+--------------------------------
The Cisco Firewall Services Module (FWSM) is not affected by any of
these vulnerabilities. Cisco PIX security appliances running software
versions 6.x are not vulnerable. IOS, IOS XR, and Cisco Unified
Boarder Elements (CUBE) are not vulnerable to these issues. No other
Cisco products are currently known to be affected by these
vulnerabilities.
Details
======
The following sections provide details to help determine if a device
may be affected by any of the vulnerabilities.
Erroneous SIP Processing Vulnerabilities
Cisco PIX and Cisco ASA devices configured for SIP inspection are
vulnerable to multiple processing errors that may result in denial of
service attacks. All Cisco PIX and Cisco ASA software releases may be
vulnerable to these SIP processing vulnerabilities. A successful
attack may result in a reload of the device.
SIP inspection is enabled with the inspect sip command.
To determine whether the Cisco PIX or Cisco ASA security appliance is
configured to support inspection of sip packets, log in to the device
and issue the CLI command show service-policy | include sip. If the
output contains the text Inspect: sip and some statistics, then the
device has a vulnerable configuration. The following example shows a
vulnerable Cisco ASA Security Appliance:
asa#show service-policy | include sip
Inspect: sip, packet 0, drop 0, reset-drop 0
asa#
These vulnerability is documented in the following Cisco Bug IDs and
has been assigned Common Vulnerabilities and Exposures (CVE)
identifier CVE-2008-2732.
* CSCsq07867
* CSCsq57091
* CSCsk60581
* CSCsq39315
IPSec Client Authentication Processing Vulnerability
Cisco PIX and Cisco ASA devices configured to terminate client based
VPN connections are vulnerable to a crafted authentication processing
vulnerability if they are running software versions 7.2, 8.0, or 8.1.
Devices that run software versions 7.0 or 7.1 are not affected by
this vulnerability.
A successful attack may result in a reload of the device.
Remote access VPN connections will have Internet Security Association
and Key Management Protocol (ISAKMP) enabled on an interface with the
crypto command, such as: crypto isakmp enable outside.
This vulnerability is documented in Cisco Bug ID CSCso69942
and has been assigned Common Vulnerabilities and Exposures (CVE)
identifier CVE-2008-2733.
SSL VPN Memory Leak Vulnerability and URI Processing Error
Vulnerability in SSL VPNs
A crafted SSL or HTTP packet may cause a denial of service condition
on a Cisco ASA device that is configured to terminate clientless VPN
connections. A successful attack may result in a reload of the
device.
Cisco ASA devices that run versions 7.2, 8.0, or 8.1 with clientless
SSL VPNs enabled may be affected by this vulnerability. Devices that
run software versions 7.0 and 7.1 are not affected by this
vulnerability.
Clientless VPN, SSL VPN Client, and AnyConnect connections are
enabled via the webvpn command. For example, the following
configuration shows a Cisco ASA with Clientless VPNs configured and
enabled. In this case the ASA will listen for VPN connections on the
default port, TCP port 443:
http server enable
!
webvpn
enable outside
Note that with this particular configuration, the device is
vulnerable to attacks coming from the outside interface due to the
enable outside command within the webvpn group configuration.
These vulnerabilities are documented in Cisco Bug ID CSCso66472
and CSCsq19369. They have been assigned Common Vulnerabilities and
Exposures (CVE) identifiers CVE-2008-2734 and CVE-2008-2735.
Potential Information Disclosure in Clientless VPNs
On Cisco ASA devices configured to terminate clientless VPN
connections, an attacker may be able to discover potentially
sensitive information such as usernames and passwords. This attack
requires an attacker to convince a user to visit a rogue web server,
reply to an e-mail, or interact with a service to successfully
exploit the vulnerability.
Cisco ASA devices running software versions 8.0 or 8.1 with
clientless VPNs enabled may be affected by this vulnerability. Cisco
ASA devices running that run software versions 7.0, 7.1, or 7.2 are
not vulnerable to this vulnerability.
Clientless SSL VPN connections are enabled via the webvpn command.
For example, the following configuration shows a Cisco ASA device
with Clientless VPNs configured and enabled. In this case the Cisco
ASA device will listen for VPN connections on the default port, TCP
port 443:
http server enable
!
webvpn
enable outside
Note that with this particular configuration, the device is
vulnerable to attacks coming from the outside interface due to the
enable outside command within the webvpn group configuration.
This vulnerability is documented in Cisco Bug ID CSCsq45636
and has been assigned Common Vulnerabilities and Exposures (CVE)
identifier CVE-2008-2736.
Vulnerability Scoring Details
============================
Cisco has provided scores for the vulnerabilities in this advisory
based on the Common Vulnerability Scoring System (CVSS). The CVSS
scoring in this Security Advisory is calculated in accordance with
CVSS version 2.0.
CVSS is a standards-based scoring method that conveys vulnerability
severity and helps determine urgency and priority of response.
Cisco has provided a base and temporal score. Customers can then
compute environmental scores to assist in determining the impact of
the vulnerability in individual networks.
Cisco has provided an FAQ to answer additional questions regarding
CVSS at:
http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html
Cisco has also provided a CVSS calculator to help compute the
environmental impact for individual networks at:
http://intellishield.cisco.com/security/alertmanager/cvss
Erroneous SIP Processing Vulnerabilities
CSCsq07867 - Memory corruption with traceback in SIP inspection code
CVSS Base Score - 7.8
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - None
Integrity Impact - None
Availability Impact - Complete
CVSS Temporal Score - 6.4
Exploitability - Functional
Remediation Level - Official Fix
Report Confidence - Confirmed
CSCsq57091 - Memory corruption and traceback when inspecting malformed SIP packets
CVSS Base Score - 7.8
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - None
Integrity Impact - None
Availability Impact - Complete
CVSS Temporal Score - 6.4
Exploitability - Functional
Remediation Level - Official Fix
Report Confidence - Confirmed
CSCsk60581 - Device reload possible when SIP inspection is enabled
CVSS Base Score - 7.8
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - None
Integrity Impact - None
Availability Impact - Complete
CVSS Temporal Score - 6.4
Exploitability - Functional
Remediation Level - Official Fix
Report Confidence - Confirmed
CSCsq39315 - Traceback when processing malformed SIP requests
CVSS Base Score - 7.8
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - None
Integrity Impact - None
Availability Impact - Complete
CVSS Temporal Score - 6.4
Exploitability - Functional
Remediation Level - Official Fix
Report Confidence - Confirmed
IPSec Client Authentication Processing Vulnerability
CSCso69942 - Traceback in Remote Access Authentication Code
CVSS Base Score - 6.8
Access Vector - Network
Access Complexity - Low
Authentication - Single
Confidentiality Impact - None
Integrity Impact - None
Availability Impact - Complete
CVSS Temporal Score - 5.6
Exploitability - Functional
Remediation Level - Official Fix
Report Confidence - Confirmed
SSL VPN Memory Leak Vulnerability
CSCso66472 - Crypto memory leak causing Clientless SSL VPNs to hang
CVSS Base Score - 7.8
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - None
Integrity Impact - None
Availability Impact - Complete
CVSS Temporal Score - 6.4
Exploitability - Functional
Remediation Level - Official Fix
Report Confidence - Confirmed
URI Processing Error Vulnerability in SSL VPNs
CSCsq19369 - URI Processing Error in Clientless SSL VPN connections
CVSS Base Score - 7.8
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - None
Integrity Impact - None
Availability Impact - Complete
CVSS Temporal Score - 6.4
Exploitability - Functional
Remediation Level - Official Fix
Report Confidence - Confirmed
Potential Information Disclosure in Clientless VPNs
CSCsq45636 - Potential Information Disclosure in Clientless SSL VPNs
CVSS Base Score - 7.1
Access Vector - Network
Access Complexity - Medium
Authentication - None
Confidentiality Impact - Complete
Integrity Impact - None
Availability Impact - None
CVSS Temporal Score - 5.9
Exploitability - Functional
Remediation Level - Official Fix
Report Confidence - Confirmed
Impact
=====
Successful exploitation of the Erroneous SIP Processing
Vulnerabilities, IPSec Client Authentication Processing
Vulnerability, SSL VPN Memory Leak Vulnerability, or URI Processing
Error Vulnerability in SSL VPNs may result in the device reloading.
This can be repeatedly exploited and may lead to a denial of service
attack.
The Potential Information Disclosure in Clientless SSL VPNs
vulnerability may allow an attacker to obtain user and group
credentials if the user interacts with a rogue system or document.
Software Versions and Fixes
==========================
When considering software upgrades, also consult
http://www.cisco.com/go/psirt and any subsequent advisories to
determine exposure and a complete upgrade solution.
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 Technical Assistance Center (TAC) or your contracted
maintenance provider for assistance.
The following list contains the first fixed software release of each
vulnerability:
+-----------------------------------------------------+
| | | Affected | First |
| Vulnerability | Bug ID | Release | Fixed |
| | | | Release |
|----------------+------------+----------+------------|
| | | 7.0 | 7.0(7)15 |
| | |----------+------------|
| | | 7.1 | 7.1(2)70 |
|Memory | |----------+------------|
| corruption | | 7.2 | Not |
| with traceback | CSCsq07867 | | vulnerable |
|in SIP | |----------+------------|
| inspection | | 8.0 | Not |
| code | | | vulnerable |
| | |----------+------------|
| | | 8.1 | Not |
| | | | vulnerable |
|----------------+------------+----------+------------|
| | | 7.0 | Not |
| | | | vulnerable |
|Memory | |----------+------------|
| corruption and | | 7.1 | Not |
| traceback when | | | vulnerable |
|inspecting |CSCsq57091 |----------+------------|
| malformed SIP | | 7.2 | 7.2(4)7 |
|packets | |----------+------------|
| | | 8.0 | 8.0(3)20 |
| | |----------+------------|
| | | 8.1 | 8.1(1)8 |
|----------------+------------+----------+------------|
| | | 7.0 | Not |
| | | | vulnerable |
| | |----------+------------|
| | | 7.1 | Not |
| Device reload | | | vulnerable |
|possible when |CSCsk60581 |----------+------------|
| SIP inspection | | 7.2 | 7.2(3)18 |
|is enabled | |----------+------------|
| | | 8.0 | 8.0(3)8 |
| | |----------+------------|
| | | 8.1 | Not |
| | | | vulnerable |
|----------------+------------+----------+------------|
| | | 7.0 | 7.0(7)16 |
| | |----------+------------|
| | | 7.1 | 7.1(2)71 |
| | |----------+------------|
| Traceback when | | 7.2 | Not |
| processing | CSCsq39315 | | vulnerable |
|malformed SIP | |----------+------------|
| requests | | 8.0 | Not |
| | | | vulnerable |
| | |----------+------------|
| | | 8.1 | Not |
| | | | vulnerable |
|----------------+------------+----------+------------|
| | | 7.0 | Not |
| | | | vulnerable |
| | |----------+------------|
| Traceback in | | 7.1 | Not |
| Remote Access | | | vulnerable |
|Authentication |CSCso69942 |----------+------------|
| Code | | 7.2 | 7.2(4)2 |
| | |----------+------------|
| | | 8.0 | 8.0(3)14 |
| | |----------+------------|
| | | 8.1 | 8.1(1)4 |
|----------------+------------+----------+------------|
| | | 7.0 | Not |
| | | | vulnerable |
| | |----------+------------|
| Crypto memory | | 7.1 | Not |
| leak causing | | | vulnerable |
|Clientless SSL |CSCso66472 |----------+------------|
| VPNs to hang | | 7.2 | 7.2(4)2 |
| | |----------+------------|
| | | 8.0 | 8.0(3)14 |
| | |----------+------------|
| | | 8.1 | 8.1(1)4 |
|----------------+------------+----------+------------|
| | | 7.0 | Not |
| | | | vulnerable |
| | |----------+------------|
| HTTP | | 7.1 | Not |
| Processing | | | vulnerable |
|Error in |CSCsq19369 |----------+------------|
| Clientless SSL | | 7.2 | Not |
| VPN | | | vulnerable |
|connections | |----------+------------|
| | | 8.0 | 8.0(3)15 |
| | |----------+------------|
| | | 8.1 | 8.1(1)5 |
|----------------+------------+----------+------------|
| | | 7.0 | Not |
| | | | vulnerable |
| | |----------+------------|
| Potential | | 7.1 | Not |
| Information | | | vulnerable |
|Disclosure in |CSCsq45636 |----------+------------|
| Clientless SSL | | 7.2 | Not |
| VPNs | | | vulnerable |
| | |----------+------------|
| | | 8.0 | 8.0(3)16 |
| | |----------+------------|
| | | 8.1 | 8.1(1)6 |
|-----------------------------+----------+------------|
| | 7.0 | 7.0(7)16 |
| |----------+------------|
| | 7.1 | 7.1(2)72 |
| |----------+------------|
| Recommended Release | 7.2 | 7.2(4)9 |
| |----------+------------|
| | 8.0 | 8.0(4) |
| |----------+------------|
| | 8.1 | 8.1(1)8 |
+-----------------------------------------------------+
Fixed Cisco PIX software can be downloaded from:
http://www.cisco.com/pcgi-bin/tablebuild.pl/pix?psrtdcat20e2
Fixed Cisco ASA software can be downloaded from:
http://www.cisco.com/pcgi-bin/tablebuild.pl/asa?psrtdcat20e2
Workarounds
==========
The following workarounds may help some customers mitigate these
vulnerabilities.
Additional mitigation techniques that can be deployed on Cisco
devices within the network are available in the Cisco Applied
Mitigation Bulletin companion document for this advisory:
http://www.cisco.com/warp/public/707/cisco-amb-20080903-asa.shtml
Erroneous SIP Processing Vulnerabilities
SIP inspection should be disabled if it is not needed and temporarily
disabling the feature will mitigate the SIP processing
vulnerabilities. SIP inspection can be disabled with the command no
inspect sip.
IPSec Authentication Processing Vulnerability
Use strong group credentials for remote access VPN connections and do
not give out the group credentials to end users.
SSL VPN Memory Leak Vulnerability and URI Processing Error
Vulnerability in SSL VPNs
IPSec clients are not vulnerable to this issue and may be used in
conjunction with strong group credentials until the device can be
upgraded.
Potential Information Disclosure in Clientless SSL VPNs
Client based VPN connections are not vulnerable to the information
disclosure vulnerability. If you are running 8.0(3)15, 8.0(3)16,
8.1(1)4, or 8.1(1)5, you may safely use client based VPN connections as
an alternative to clientless VPNs.
Obtaining Fixed Software
=======================
Cisco has released free software updates that address these
vulnerabilities. Prior to deploying software, customers should
consult their maintenance provider or check the software for feature
set compatibility and known issues specific to their environment.
Customers may only install and expect support for the feature sets
they have purchased. By installing, downloading, accessing or
otherwise using such software upgrades, customers agree to be bound
by the terms of Cisco's software license terms found at:
http://www.cisco.com/en/US/products/prod_warranties_item09186a008088e31f.html
or as otherwise set forth at Cisco.com Downloads at:
http://www.cisco.com/public/sw-center/sw-usingswc.shtml
Do not contact psirt@cisco.com or security-alert@cisco.com for
software upgrades.
Customers with Service Contracts
+-------------------------------
Customers with contracts should obtain upgraded software through
their regular update channels. For most customers, this means that
upgrades should be obtained through the Software Center on Cisco's
worldwide website at http://www.cisco.com.
Customers using Third Party Support Organizations
+------------------------------------------------
Customers whose Cisco products are provided or maintained through
prior or existing agreements with third-party support organizations,
such as Cisco Partners, authorized resellers, or service providers
should contact that support organization for guidance and assistance
with the appropriate course of action in regards to this advisory.
The effectiveness of any workaround or fix is dependent on specific
customer situations, such as product mix, network topology, traffic
behavior, and organizational mission. Due to the variety of affected
products and releases, customers should consult with their service
provider or support organization to ensure any applied workaround or
fix is the most appropriate for use in the intended network before it
is deployed.
Customers without Service Contracts
+----------------------------------
Customers who purchase direct from Cisco but do not hold a Cisco
service contract, and customers who purchase through third-party
vendors but are unsuccessful in obtaining fixed software through
their point of sale should acquire upgrades by contacting the Cisco
Technical Assistance Center (TAC). TAC contacts are as follows.
* +1 800 553 2447 (toll free from within North America)
* +1 408 526 7209 (toll call from anywhere in the world)
* e-mail: tac@cisco.com
Customers should have their product serial number available and be
prepared to give the URL of this notice as evidence of entitlement to
a free upgrade. Free upgrades for non-contract customers must be
requested through the TAC.
Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml
for additional TAC contact information, including localized telephone
numbers, and instructions and e-mail addresses for use in various
languages.
Exploitation and Public Announcements
====================================
The Cisco PSIRT is not aware of any public announcements or malicious
use of the vulnerability described in this advisory.
These vulnerabilities were reported to Cisco by customers that
experienced these issues during normal operation of their equipment
and through internal testing efforts.
Status of this Notice: FINAL
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE
INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS
AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS
DOCUMENT AT ANY TIME.
A stand-alone copy or Paraphrase of the text of this document that
omits the distribution URL in the following section is an
uncontrolled copy, and may lack important information or contain
factual errors.
Distribution
===========
This advisory is posted on Cisco's worldwide website at:
http://www.cisco.com/warp/public/707/cisco-sa-20080903-asa.shtml
In addition to worldwide web posting, a text version of this notice
is clear-signed with the Cisco PSIRT PGP key and is posted to the
following e-mail and Usenet news recipients.
* cust-security-announce@cisco.com
* first-bulletins@lists.first.org
* bugtraq@securityfocus.com
* vulnwatch@vulnwatch.org
* cisco@spot.colorado.edu
* cisco-nsp@puck.nether.net
* full-disclosure@lists.grok.org.uk
* comp.dcom.sys.cisco@newsgate.cisco.com
Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on
mailing lists or newsgroups. Users concerned about this problem are
encouraged to check the above URL for any updates.
Revision History
===============
+---------------------------------------+
| Revision | | Initial |
| 1.0 | 2008-Sept-03 | public |
| | | release. |
+---------------------------------------+
Cisco Security Procedures
========================
Complete information on reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and
registering to receive security information from Cisco, is available
on Cisco's worldwide website at:
http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html
This includes instructions for press inquiries regarding Cisco security
notices. All Cisco security advisories are available at:
http://www.cisco.com/go/psirt
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