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

07.12.07

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 platforms. At boot and shutdown time, these scripts are run by the init program to start and stop various system services.

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.

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.

DETECTION

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

WORKAROUND

iDefense is currently unaware of any workarounds for this issue.

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

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.

DISCLOSURE TIMELINE

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

CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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LEGAL NOTICES

Copyright © 2007 Verisign, Inc.

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Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.