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Vulnerability Note VU#426456

gpm creates temporary files insecurely

Overview

gpm version 1.19.3, which usually runs as root, is vulnerable due to a flaw that allows a local user to exploit a race condition to corrupt files that gpm uses.

I. Description

gpm (General Purpose Mouse) is a program that lets you use the mouse in console mode when not using XWindows. It is usually included in Linux distributions, and can be started from the command line or in the startup script /etc/rc.d/rc.local. A vulnerability in gpm version 1.19.3 allows a local user to exploit a race condition to corrupt files that gpm uses. The flaw exists because gpm creates files in the /tmp directory using predictable filenames without checking whether a file with that name already exists. Malicious local users can therefore create a symbolic link to a file that will be used by gpm. When gpm is run, the creation of the file fails (since it already exists) and gpm uses the symbolically linked file for its processing. The malicious user can then overwrite or append to the file as it is being used by the privileged gpm program.

II. Impact

Malicious users can destroy the integrity of or deny access to files processed by gpm, which usually runs as root.

III. Solution

Upgrade affected Linux distributions.

Systems Affected

VendorStatusDate NotifiedDate Updated
ImmunixVulnerable1-Jun-2001
MandrakeSoftVulnerable1-Jun-2001
RedHatVulnerable1-Jun-2001

References

http://www.securityfocus.com/bid/2188
http://download.immunix.org/ImmunixOS/7.0-beta/updates/IMNX-2000-70-016-01
http://archives.neohapsis.com/archives/linux/immunix/2001-q1/0010.html
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2001-0116
http://www.linux-mandrake.com/en/security/2001/MDKSA-2001-006.php3?dis=6

Credit

Thanks to Greg Kroah-Hartman of WireX for discovering this vulnerability. Thanks also to BugTraq for a good description of the underlying problem.

This document was written by Andy Moore.

Other Information

Date Public:2001-01-10
Date First Published:2001-06-08
Date Last Updated:2001-06-22
CERT Advisory: 
CVE-ID(s):CVE-2001-0116
NVD-ID(s):CVE-2001-0116
US-CERT Technical Alerts: 
Severity Metric:2.66
Document Revision:13

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Copyright 2001 Carnegie Mellon University
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