Red Hat Linux Advisory: GDMAug 22, 2003, 00:59 (0 Talkback[s])
Red Hat Security Advisory
Updated GDM packages are available which correct a bug allowing local users to read any text files on the system, and a denial of service issue if XDMCP is enabled.
2. Relevant releases/architectures:
Red Hat Linux 7.1 - i386
3. Problem description:
GDM is the GNOME Display Manager for X.
Versions of GDM prior to 18.104.22.168 contain a bug where GDM will run as root when examining the ~/.xsession-errors file when using the "examine session errors" feature, allowing local users the ability to read any text file on the system by creating a symlink. The Common Vulnerabilities and Exposures project (cve.mitre.org/) has assigned the name CAN-2003-0547 to this issue.
Red Hat Linux 8.0 and 9 are vulnerable to this issue. Versions of GDM in earlier releases did not have the "examine session errors" feature and therefore are not vulnerable to this issue.
Also addressed by these erratum packages are two problems in the X Display Manager Control Protocol (XDMCP) which allow a denial of service attack (DoS) by crashing the gdm daemon. The Common Vulnerabilities and Exposures project (cve.mitre.org/) has assigned the names CAN-2003-0548 and CAN-2003-0549 to these issues.
This attack is only possible if XDMCP is enabled. XDMCP is not enabled by default in Red Hat Linux distributions, and as documented XDMCP should only ever be run on trusted networks.
Users of GDM are advised to upgrade to these erratum packages which disable the "examine session errors" feature and contain backported security fixes for the XDMCP issues.
Before applying this update, make sure all previously released errata relevant to your system have been applied.
To update all RPMs for your particular architecture, run:
rpm -Fvh [filenames]
where [filenames] is a list of the RPMs you wish to upgrade. Only those RPMs which are currently installed will be updated. Those RPMs which are not installed but included in the list will not be updated. Note that you can also use wildcards (*.rpm) if your current directory only contains the desired RPMs.
Please note that this update is also available via Red Hat Network. Many people find this an easier way to apply updates. To use Red Hat Network, launch the Red Hat Update Agent with the following command:
This will start an interactive process that will result in the appropriate RPMs being upgraded on your system.
5. RPMs required:
Red Hat Linux 7.1:
Red Hat Linux 7.1 for iSeries (64 bit):
Red Hat Linux 7.1 for pSeries (64 bit):
Red Hat Linux 7.2:
Red Hat Linux 7.3:
Red Hat Linux 8.0:
Red Hat Linux 9:
MD5 sum Package Name
These packages are GPG signed by Red Hat for security. Our key is available from http://www.redhat.com/security/keys.html
You can verify each package with the following command:
rpm --checksig -v <filename>
If you only wish to verify that each package has not been corrupted or tampered with, examine only the md5sum with the following command:
The Red Hat security contact is <firstname.lastname@example.org>. More contact details at http://www.redhat.com/solutions/security/news/contact.html
Copyright 2003 Red Hat, Inc.
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