Security Advisory (MDKSA-2003:085): gdm

[aru]

MandrakeSoft Security Advisory MDKSA-2003:085 : gdm

 

August 21st, 2003

Updated gdm packages fix vulnerabilities

 

Several vulnerabilities were discovered in versions of gdm prior to 2.4.1.6. 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 2.4.1.6 which is not vulnerable to any of these problems. Also note that XDMCP support is disabled by default in gdm.

 

 

The released versions of Mandrake GNU/Linux affected are:

• 9.0

 

[*] 9.1

 

[*] Corporate Server 2.1

Full information about this advisory, including the updated packages, is available at:

www.mandrakesecure.net/en/advisories/advisory.php?name=MDKSA-2003:085

 

Other references:

http://cve.mitre.org/cgi-bin/cvename.cgi?n...e=CAN-2003-0547

http://cve.mitre.org/cgi-bin/cvename.cgi?n...e=CAN-2003-0548

http://cve.mitre.org/cgi-bin/cvename.cgi?n...e=CAN-2003-0549

 

Posted automatically by aru (mdksec2mub v0.0.6)