Vulnerability Note VU#846832

Overview

The glibc implementation of unsetenv() fails to properly remove one of two successive occurrences of the same environment variable if the variable is redundently passed to a program.

Description

The glibc implementation of unsetenv(), if called to remove an environment variable that occurs two times in succession on the environment variable list, will fail to remove one of the occurences due to an off-by-one error in the implementation.

Impact

An attacker can pass multiple occurrences of a sensitive environment variable (such as LD_LIBRARY_PATH, LD_PRELOAD, etc.) to a setuid root program. Even if glibc forces that program to ignore these variables, they may be passed along to a program called from the setuid root program. Using this indirect execution, an attacker might cause malicious code to be executed as root.

Solution

Apply vendor patches; see the Systems Affected section below.

Systems Affected (Learn More)

Vendor	Status	Date Notified	Date Updated
Conectiva	Affected	31 Aug 2000	16 May 2001
Debian	Affected	31 Aug 2000	13 Sep 2002
MandrakeSoft	Affected	29 Aug 2000	16 May 2001
TurboLinux	Affected	31 Aug 2000	16 May 2001

If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group	Score	Vector
Base	N/A	N/A
Temporal	N/A	N/A
Environmental	N/A	N/A

References

• http://www.securityfocus.com/bid/648
• http://www.securityfocus.com/bid/1639

Credit

The original report of this vulnerability was by Tymm Twillman <tymm@coe.missouri.edu>.

This document was last modified by Tim Shimeall.

Other Information

• CVE IDs: CVE-2000-0824
• Date Public: 17 Sep 99
• Date First Published: 17 May 2001
• Date Last Updated: 13 Sep 2002
• Severity Metric: 7.09
• Document Revision: 9