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AUSCERT External Security Bulletin Redistribution
ESB-2006.0742 -- [UNIX/Linux][Solaris]
Security Vulnerability in X Display Manager (xdm(1)) Xsession Script
31 January 2007
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AusCERT Security Bulletin Summary
---------------------------------
Product: xdm
Publisher: Sun Microsystems
Operating System: Solaris 10
Solaris 9
Solaris 8
UNIX variants (UNIX, Linux, OSX)
Impact: Overwrite Arbitrary Files
Read-only Data Access
Access: Existing Account
CVE Names: CVE-2006-5215 CVE-2006-5214
Original Bulletin:
http://sunsolve.sun.com/search/printfriendly.do?assetkey=1-26-102652-1
Comment: This advisory references vulnerabilities in products which run on
platforms other than Solaris. It is recommended that administrators
running xdm check for an updated version of the software from their
vendor.
Revision History: January 31 2007: Patches are now available
October 18 2006: Updated Contributing Factors and
Workaround sections and added CVE Name
October 16 2006: Updates to Relief/Workaround section
October 9 2006: Initial Release
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Sun(sm) Alert Notification
* Sun Alert ID: 102652
* Synopsis: Security Vulnerability in X Display Manager (xdm(1))
Xsession Script
* Category: Security
* Product: Solaris 9 Operating System, Solaris 10 Operating System,
Solaris 8 Operating System
* BugIDs: 6388471, 6423858
* Avoidance: Patch, Workaround
* State: Resolved
* Date Released: 06-Oct-2006, 29-Jan-2007
* Date Closed: 29-Jan-2007
* Date Modified: 12-Oct-2006, 16-Oct-2006, 14-Dec-2006, 29-Jan-2007
1. Impact
The X Display Manager (xdm(1)) manages a collection of X displays
which may be on the local host or remote servers. A race condition in
the Xsession script executed by xdm(1) my lead to either of the
following issues:
1. A local unprivileged user may be able to view the xdm(1) error log
file, $HOME/.xsession-errors, of another user (BugID 6388471).
This issue is also described in Xorg bug 5897:
https://bugs.freedesktop.org/show_bug.cgi?id=5897
2. A local unprivileged user may be able to view the alternate xdm(1)
error log file, ${TMP-/tmp}/xses-$USER, of another user. In addition,
when this alternate log file is in use, a local unprivileged user may
be able to erase the contents of arbitrary files which are writable by
another user. This alternate log file is only used if the
$HOME/.xsession-errors file could not be created (BugID 6423858).
This issue is also described in Xorg bug 5898:
https://bugs.freedesktop.org/show_bug.cgi?id=5898
2. Contributing Factors
This issue can occur in the following releases:
SPARC Platform
* Solaris 8 without patch 111844-04
* Solaris 9 without patch 124830-01
* Solaris 10 without patch 124457-01
x86 Platform
* Solaris 8 without patch 111845-04
* Solaris 9 without patch 124831-01
* Solaris 10 without patch 124458-01
3. Symptoms
There are no predictable symptoms that would indicate the described
issues have been exploited.
4. Relief/Workaround
To work around the described issues (until a patch is available),
consider one of the two following workarounds:
A) Use an alternate login mechanism such as dtlogin(1) or if using
Solaris 10, gdm(1).
or:
B) Modify the xdm(1) configuration file, xdm-config, and create a new
Xsession file using the following commands as the root user:
# cd /usr/openwin/lib/X11/xdm
# mv xdm-config xdm-config.orig
# sed -e 's/cp \/dev\/null "$errfile"/umask 077 \&\& cp \/dev\/null "$errfi
le"/' Xsession > /etc/X11/Xsession
# sed -e 's/\/usr\/openwin\/lib\/X11\/xdm\/Xsession/\/etc\/X11\/Xsession/'
xdm-config.orig > xdm-config
then restore executable permissions to the file by running the
following command:
# chmod 755 Xsession
5. Resolution
This issue is addressed in the following releases:
SPARC Platform
* Solaris 8 with patch 111844-04 or later
* Solaris 9 with patch 124830-01 or later
* Solaris 10 with patch 124457-01 or later
x86 Platform
* Solaris 8 with patch 111845-04 or later
* Solaris 9 with patch 124831-01 or later
* Solaris 10 with patch 124458-01 or later
Change History
12-Oct-2006:
* Updated Relief/Workaround section
16-Oct-2006:
* Updated Contributing Factors and Workaround sections
14-Dec-2006:
* Updated Contributing Factors and Resolution sections
29-Jan-2007:
* Updated Contributing Factors and Resolution sections
* State: Resolved
This Sun Alert notification is being provided to you on an "AS IS"
basis. This Sun Alert notification may contain information provided by
third parties. The issues described in this Sun Alert notification may
or may not impact your system(s). Sun makes no representations,
warranties, or guarantees as to the information contained herein. ANY
AND ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR
NON-INFRINGEMENT, ARE HEREBY DISCLAIMED. BY ACCESSING THIS DOCUMENT
YOU ACKNOWLEDGE THAT SUN SHALL IN NO EVENT BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES THAT ARISE
OUT OF YOUR USE OR FAILURE TO USE THE INFORMATION CONTAINED HEREIN.
This Sun Alert notification contains Sun proprietary and confidential
information. It is being provided to you pursuant to the provisions of
your agreement to purchase services from Sun, or, if you do not have
such an agreement, the Sun.com Terms of Use. This Sun Alert
notification may only be used for the purposes contemplated by these
agreements.
Copyright 2000-2006 Sun Microsystems, Inc., 4150 Network Circle, Santa
Clara, CA 95054 U.S.A. All rights reserved
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