GNOME Display Manager (gdm) 2.x before 2.32.1 allows local users to change the ownership of arbitrary files via a symlink attack on a (1) dmrc or (2) face icon file under /var/cache/gdm/.

The remote host is affected by the vulnerability described in GLSA-201412-09 (Multiple packages, Multiple vulnerabilities fixed in 2011)

    Vulnerabilities have been discovered in the packages listed below.
      Please review the CVE identifiers in the Reference section for details.
      FMOD Studio       PEAR Mail       LVM2       GnuCash       xine-lib       Last.fm Scrobbler       WebKitGTK+       shadow tool suite       PEAR       unixODBC       Resource Agents       mrouted       rsync       XML Security Library       xrdb       Vino       OProfile       syslog-ng       sFlow Toolkit       GNOME Display Manager       libsoup       CA Certificates       Gitolite       QtCreator       Racer   Impact :

    A context-dependent attacker may be able to gain escalated privileges,       execute arbitrary code, cause Denial of Service, obtain sensitive       information, or otherwise bypass security restrictions.
  Workaround :

    There are no known workarounds at this time.

Local users could trick gdm into changing ownership of arbitrary files by placing symlinks in the user session cache (CVE-2011-0727).

From Red Hat Security Advisory 2011:0395 :

Updated gdm packages that fix one security issue are now available for Red Hat Enterprise Linux 6.

The Red Hat Security Response Team has rated this update as having moderate security impact. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available from the CVE link in the References section.

The GNOME Display Manager (GDM) provides the graphical login screen, shown shortly after boot up, log out, and when user-switching.

A race condition flaw was found in the way GDM handled the cache directories used to store users' dmrc and face icon files. A local attacker could use this flaw to trick GDM into changing the ownership of an arbitrary file via a symbolic link attack, allowing them to escalate their privileges. (CVE-2011-0727)

Red Hat would like to thank Sebastian Krahmer of the SuSE Security Team for reporting this issue.

All users should upgrade to these updated packages, which contain a backported patch to correct this issue. GDM must be restarted for this update to take effect. Rebooting achieves this, but changing the runlevel from 5 to 3 and back to 5 also restarts GDM.

The GNOME Display Manager (GDM) provides the graphical login screen, shown shortly after boot up, log out, and when user-switching.

A race condition flaw was found in the way GDM handled the cache directories used to store users' dmrc and face icon files. A local attacker could use this flaw to trick GDM into changing the ownership of an arbitrary file via a symbolic link attack, allowing them to escalate their privileges. (CVE-2011-0727)

We would like to thank Sebastian Krahmer of the SuSE Security Team for reporting this issue.

This update addresses a local root exploit for GDM.

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

A vulnerability has been found and corrected in gdm :

GNOME Display Manager (gdm) 2.x before 2.32.1 allows local users to change the ownership of arbitrary files via a symlink attack on a (1) dmrc or (2) face icon file under /var/cache/gdm/ (CVE-2011-0727).

The updated packages have been patched to correct this issue.

This update addresses a local root exploit.

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Sebastian Krahmer discovered that GDM (GNOME Display Manager) did not properly drop privileges when handling the cache directories used to store users' dmrc and face icon files. This could allow a local attacker to change the ownership of arbitrary files, thereby gaining root privileges.

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Sebastian Krahmer reports :

It was discovered that the GNOME Display Manager (gdm) cleared the cache directory, which is owned by an unprivileged user, with the privileges of the root user. A race condition exists in gdm where a local user could take advantage of this by writing to the cache directory between ending the session and the signal to clean up the session, which could lead to the execution of arbitrary code as the root user.

The remote Redhat Enterprise Linux 6 host has packages installed that are affected by a vulnerability as referenced in the RHSA-2011:0395 advisory.

  - gdm: privilege escalation vulnerability (CVE-2011-0727)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Sebastian Krahmer discovered that GDM 3, the GNOME Display Manager, does not properly drop privileges when manipulating files related to the logged-in user. As a result, local users can gain root privileges.

The oldstable distribution (lenny) does not contain a gdm3 package.
The gdm package is not affected by this issue.

ID	Name	Product	Family	Severity
79962	GLSA-201412-09 : Multiple packages, Multiple vulnerabilities fixed in 2011	Nessus	Gentoo Local Security Checks	critical
75847	openSUSE Security Update : gdm (openSUSE-SU-2011:0275-1)	Nessus	SuSE Local Security Checks	medium
75511	openSUSE Security Update : gdm (openSUSE-SU-2011:0275-1)	Nessus	SuSE Local Security Checks	medium
68241	Oracle Linux 6 : gdm (ELSA-2011-0395)	Nessus	Oracle Linux Local Security Checks	medium
60998	Scientific Linux Security Update : gdm on SL6.x i386/x86_64	Nessus	Scientific Linux Local Security Checks	medium
53437	Fedora 13 : gdm-2.30.2-2.fc13 (2011-4351)	Nessus	Fedora Local Security Checks	medium
53349	Mandriva Linux Security Advisory : gdm (MDVSA-2011:070)	Nessus	Mandriva Local Security Checks	medium
53265	Fedora 14 : gdm-2.32.1-2.fc14 (2011-4335)	Nessus	Fedora Local Security Checks	medium
53238	Ubuntu 9.10 / 10.04 LTS / 10.10 : gdm vulnerability (USN-1099-1)	Nessus	Ubuntu Local Security Checks	medium
53217	FreeBSD : gdm -- privilege escalation vulnerability (c6fbd447-59ed-11e0-8d04-0015f2db7bde)	Nessus	FreeBSD Local Security Checks	medium
53207	RHEL 6 : gdm (RHSA-2011:0395)	Nessus	Red Hat Local Security Checks	critical
53198	Debian DSA-2205-1 : gdm3 - privilege escalation	Nessus	Debian Local Security Checks	medium

Detections

Analytics

CVE-2011-0727

critical

Tenable Plugins

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critical

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