Vulnerability Note VU#943633

FreeBSD can be compromised locally via signal handlers

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.

I. 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 After this has occured, the kernel should clear the signal handlers because they are no longer valid.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.

II. Impact

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

III. Solution

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

Systems Affected

Vendor	Status	Date Notified
Cray Inc.	Not Vulnerable	4-Oct-2001
FreeBSD	Vulnerable	14-Sep-2001
Hewlett-Packard Company	Not Vulnerable	21-Sep-2001

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

Date Public:	2001-07-10
Date First Published:	2001-09-14
Date Last Updated:	2002-12-12
CERT Advisory:
CVE-ID(s):	CVE-2001-1180
NVD-ID(s):	CVE-2001-1180
US-CERT Technical Alerts:
Metric:	29.25
Document Revision:	30

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