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Home » Hacking News » Mandrake MDKSA-2003:085: gdm multiple vulnerabilities

Mandrake MDKSA-2003:085: gdm multiple vulnerabilities

by Nikola Strahija on August 21st, 2003 Several vulnerabilities were discovered in versions of gdm prior to These vulnerabilities could allow local attacker to read the file owned by root user and could make the daemon cause a SEGV.

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Mandrake Linux Security Update Advisory

Package name: gdm
Advisory ID: MDKSA-2003:085
Date: August 21st, 2003

Affected versions: 9.0, 9.1, Corporate Server 2.1

Problem Description:

Several vulnerabilities were discovered in versions of gdm prior to The first vulnerability is that any user can read any text
file on the system due to code originally written to be run as the user
logging in was in fact being run as the root user. This code is what
allows the examination of the ~/.xsession-errors file. If a user makes
a symlink from this file to any other file on the system during the
session and ensures that the session lasts less than ten seconds, the
user can read the file provided it was readable as a text file.

Another two vulnerabilities were found in the XDMCP code that could be
exploited to crash the main gdm daemon which would inhibit starting
any new sessions (although the current session would be unaffected).
The first problem here is due to the indirect query structure being
used right after being freed due to a missing 'continue' statement in a
loop; this happens if a choice of server expired and the client tried
to connect.

The second XDMCP problem is that when authorization data is being
checked as a string, the length is not checked first. If the data is
less than 18 bytes long, the daemon may wander off the end of the
string a few bytes in the strncmp which could cause a SEGV.

These updated packages bring gdm to version which is not
vulnerable to any of these problems. Also note that XDMCP support is
disabled by default in gdm.


Updated Packages:

Corporate Server 2.1:
47a2d84bfff0e842657e789e085b434d corporate/2.1/RPMS/gdm-
8536d89374219e42ad6ca6c441ffb0d1 corporate/2.1/RPMS/gdm-Xnest-
35ab7f8231548f1daa4571bfb5e77054 corporate/2.1/SRPMS/gdm-

Corporate Server 2.1/x86_64:
252fc231c85e88411ca50a05f0404688 x86_64/corporate/2.1/RPMS/gdm-
3f8b47c14e0d7fc4c2d76171e3ee0b5a x86_64/corporate/2.1/RPMS/gdm-Xnest-
35ab7f8231548f1daa4571bfb5e77054 x86_64/corporate/2.1/SRPMS/gdm-

Mandrake Linux 9.0:
47a2d84bfff0e842657e789e085b434d 9.0/RPMS/gdm-
8536d89374219e42ad6ca6c441ffb0d1 9.0/RPMS/gdm-Xnest-
35ab7f8231548f1daa4571bfb5e77054 9.0/SRPMS/gdm-

Mandrake Linux 9.1:
9d8a97cc5f475f16eeb73caa9d7d8e6b 9.1/RPMS/gdm-
4f866c5b5b4903d1b0751bcb6dc28d0f 9.1/RPMS/gdm-Xnest-
91f0ff2421135e32f604d6cb82081439 9.1/SRPMS/gdm-

Mandrake Linux 9.1/PPC:
0cb8fbd74766c4d0036cab36d57b6081 ppc/9.1/RPMS/gdm-
fb0df358c4d6c9a7cf3982c4d3258004 ppc/9.1/RPMS/gdm-Xnest-
91f0ff2421135e32f604d6cb82081439 ppc/9.1/SRPMS/gdm-

Bug IDs fixed (see for more information):

To upgrade automatically, use MandrakeUpdate or urpmi. The verification
of md5 checksums and GPG signatures is performed automatically for you.

A list of FTP mirrors can be obtained from:

All packages are signed by MandrakeSoft for security. You can obtain
the GPG public key of the Mandrake Linux Security Team by executing:

gpg --recv-keys --keyserver 0x22458A98

Please be aware that sometimes it takes the mirrors a few hours to

You can view other update advisories for Mandrake Linux at:

MandrakeSoft has several security-related mailing list services that
anyone can subscribe to. Information on these lists can be obtained by

If you want to report vulnerabilities, please contact

Type Bits/KeyID Date User ID
pub 1024D/22458A98 2000-07-10 Linux Mandrake Security Team

Version: GnuPG v1.0.7 (GNU/Linux)


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