Red Hat Enterprise Linux init.d XFS Script chown Race Condition
Vulnerability

iDefense Security Advisory 07.12.07
http://labs.idefense.com/intelligence/vulnerabilities/
Jul 12, 2007

I. BACKGROUND

XFS is the X Font Server, and is used to render fonts for the X Window
System. "init.d" refers to the startup and shutdown scripts used by
Linux distributions. These scripts are run by the init process to start
and stop various system services.

II. DESCRIPTION

Local exploitation of a race condition vulnerability in Red Hat Inc.'s
Enterprise Linux init.d XFS script allows an attacker to elevate their
privileges to root.

The XFS script is vulnerable to a race condition when it is started by
init, or by a system administrator. Specifically, it insecurely changes
the file permissions of a temporary file. This allows an attacker to
make any file on the system world writable.

III. ANALYSIS

Exploitation of this vulnerability results in an attacker gaining root
privileges on the affected system.

However, in order to exploit this, it is necessary for either the system
to be rebooted, or for the administrator to manually restart the XFS.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in Red Hat
Enterprise Linux version 4, and Fedora Core 6. Other versions may also
be affected.

V. WORKAROUND

iDefense is currently unaware of any workarounds for this issue.

VI. VENDOR RESPONSE

Red Hat has released errata updates for versions 4 and 5 of their
Enterprise Linux software. More information is available at the URLs
shown below.

https://rhn.redhat.com/errata/RHSA-2007-0519.html
https://rhn.redhat.com/errata/RHSA-2007-0520.html

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-3103 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for
security problems.

VIII. DISCLOSURE TIMELINE

06/05/2007  Initial vendor notification
06/06/2007  Initial vendor response
07/12/2007  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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X. LEGAL NOTICES

Copyright © 2007 iDefense, Inc.

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