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The U.S. Department of Energy
Computer Incident Advisory Capability
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INFORMATION BULLETIN
HP-UX ppl Core Dump Vulnerability
February 18, 1997 22:00 GMT Number H-32
______________________________________________________________________________
PROBLEM: A vulnerability exists in the ppl(1) program.
PLATFORM: HP-UX 9.x and 10.x
DAMAGE: This vulnerability may allow local users to gain root
privileges.
SOLUTION: Until patches are available, take the steps outlined in section
3 as soon as possible.
______________________________________________________________________________
VULNERABILITY Exploit details involving this vulnerability have been made
ASSESSMENT: publicly available.
______________________________________________________________________________
[ Start AUSCERT Advisory ]
===========================================================================
AA-97.07 AUSCERT Advisory
HP-UX ppl core dump vulnerability
18 February 1997
Last Revised: --
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AUSCERT has received information that a vulnerability exists in the
ppl(1) program under HP-UX 9.x and 10.x.
This vulnerability may allow local users to gain root privileges.
Exploit information involving this vulnerability has been made publicly
available.
The patches listed in HP security bulletin #00053, 13 February 1997,
"Security Vulnerability in the ppl executable", do not correct this
problem.
Currently there are no vendor patches available that address this
vulnerability. AUSCERT recommends that sites take the steps outlined in
section 3 as soon as possible.
This advisory will be updated as more information becomes available.
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1. Description
AUSCERT has received information that a vulnerability exists in the
HP-UX ppl(1) program used to perform point-to-point serial networking
using SLIP or CSLIP.
ppl is a setuid root program. While ppl is executing with root
privileges, it is possible for local users to force ppl to core dump.
As users have the ability to manipulate the location of the core, this
vulnerability may be used to create or overwrite any file on the
system.
This vulnerability is known to exist in HP-UX 9.x and 10.x.
The patches listed in HP security bulletin #00053, 13 February 1997,
"Security Vulnerability in the ppl executable", do not correct this
problem. They address other security vulnerabilities.
Exploit information involving this vulnerability has been made publicly
available.
The default location for ppl under HP-UX 9.x and 10.x is /usr/bin.
2. Impact
Local users may be able to create or overwrite arbitrary files on
the system. This can be leveraged to gain root privileges.
3. Workarounds/Solution
AUSCERT recommends that sites prevent the exploitation of the
vulnerability in ppl by immediately applying the workaround given in
Section 3.1.
If the ppl functionality is required for non privileged users, AUSCERT
recommends that access be restricted to a trusted set of users as
given in Section 3.2.
Currently there are no vendor patches available that address this
vulnerability. AUSCERT recommends that official vendor patches be
installed when they are made available.
3.1 Remove setuid and execute permissions
Until official vendor patches are made available, sites should remove
the setuid root and execute permissions from ppl. To do this,
the following command should be run as root:
# chmod 400 /usr/bin/ppl
# ls -l /usr/bin/ppl
-r-------- 1 root bin 98304 Jan 24 08:13 /usr/bin/ppl
Note that this will remove the ability for any user to run this
program.
3.2 Restrict ppl access
If the ppl functionality is required by a small set of trusted users,
sites may wish to restrict the execution of ppl to that group of users.
For example, if the Unix group "trusted" exists and contains only
those users allowed to use the ppl functionality, the following
commands will restrict its use:
# chgrp trusted /usr/bin/ppl
# chmod 4550 /usr/bin/ppl
# ls -l /usr/bin/ppl
-r-sr-x--- 1 root trusted 98304 Jan 24 08:13 /usr/bin/ppl
Note access to any account in the "trusted" group will allow the ppl
package to be exploited.
4. Previous patches
During the installation of HP-UX patches, copies of files being
replaced are saved in case the patches need to be backed out of. The
original versions of patched files are stored in the following
locations:
HP-UX 9.x: /system/<PATCH-NAME>/orig/
HP-UX 10.x: /var/adm/sw/patch/<PATCH_NAME>/
If patches for vulnerable programs have been previously installed,
copies of the vulnerable programs may be available in the above
locations. Sites should ensure the directories have permissions
which restrict access to the patch areas.
5. Additional measures
Most Unix systems ship with numerous programs which have setuid or
setgid privileges. Often the functionality supplied by these
privileged programs is not required by many sites. The large number
of privileged programs that are shipped by default are to cater for
all possible uses of the system.
AUSCERT encourages sites to examine all the setuid/setgid programs
and determine the necessity of each program. If a program does not
absolutely require the setuid/setgid privileges to operate (for
example, it is only run by the root user), the setuid/setgid
privileges should be removed. Furthermore, if a program is not
required at your site, then all execute permissions should be removed.
A sample command to find all setuid/setgid programs is (run as root):
# find / \( -perm -4000 -o -perm -2000 \) -type f -exec ls -l {} \;
It is AUSCERT's experience that many vulnerability are being discovered
in setuid/setgid programs which are not necessary for the correct
operation of most systems. Sites can increase their security
by removing unnecessary setuid/setgid programs.
For example, the functionality provided by the ppl program is
not needed by many sites. If sites had previously disabled this
program, they would not have been susceptible to this latest
vulnerability.
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[ End AUSCERT Advisory ]
_____________________________________________________________________________
CIAC wishes to acknowledge the contributions of AUSCERT & Hewlett-Packard for
the information contained in this bulletin.
_____________________________________________________________________________
CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
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global organization established to foster cooperation and coordination
among computer security teams worldwide.
CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
Voice: +1 510-422-8193
FAX: +1 510-423-8002
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E-mail: ciac@llnl.gov
For emergencies and off-hour assistance, DOE, DOE contractor sites,
and the NIH may contact CIAC 24-hours a day. During off hours (5PM -
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or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two
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duty person, and the secondary PIN number, 8550074 is for the CIAC
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Previous CIAC notices, anti-virus software, and other information are
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This document was prepared as an account of work sponsored by an
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