Vulnerability Note VU#943633

Overview

The FreeBSD operating system does not adequately clear signal handlers subsequent to a process calling exec() on a setuid program. This vulnerability can allow a local attacker to execute arbitrary code as root.

Description

The unix fork() function's purpose is to create a new process from an existing process. The new process is called the child process, and the existing process is called the parent. When a process forks, it inherits the parent's signal handling settings. The unix exec() function's purpose is to replace the current process image with a new process image. After this has occured, the kernel should clear the signal handlers because they are no longer valid. Because the FreeBSD operating system does not adequately clear signal handlers subsequent to a process calling exec(), an attacker can execute arbitrary code as root.

Impact

An local attacker may be able to execute arbitrary code as root.

Solution

Apply a patch from your vendor or upgrade your operating system to FreeBSD 4.3-STABLE.

Systems Affected (Learn More)

Vendor	Status	Date Notified	Date Updated
FreeBSD	Affected	02 Jul 2001	14 Sep 2001
Cray Inc.	Not Affected	-	04 Oct 2001
Hewlett-Packard Company	Not Affected	14 Sep 2001	21 Sep 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

• ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-01:42.signal.v1.1.asc
• http://www.guninski.com/vvfreebsd.html
• http://www.securityfocus.com/bid/3007

Credit

The CERT Coordination Center thanks Georgi Guninski for discovering this vulnerability and the FreeBSD project for providing a patch to address the vulnerability.

This document was written by Ian A. Finlay.

Other Information

• CVE IDs: CVE-2001-1180
• Date Public: 10 Jul 2001
• Date First Published: 14 Sep 2001
• Date Last Updated: 12 Dec 2002
• Severity Metric: 29.25
• Document Revision: 30