Secunia

Description

A vulnerability has been identified in FreeBSD, which can be exploited by malicious, local users to cause a DoS (Denial of Service) on a vulnerable system or potentially escalate privileges.

The vulnerability is caused due to some mechanisms not validating signal numbers, which may cause the kernel to attempt to send signals with negative or out-of-range numbers. This can be exploited to cause the system to crash.

However, in FreeBSD 5.x the vulnerability may also be exploited to modify kernel memory, which can be exploited to gain escalated privileges. This requires that the "INVARIANTS" kernel option is disabled (default setting).

Reportedly, the errors are present in the "ptrace()" system call and the "spigot" video capture device driver.

Solution
Upgrade vulnerable systems to 4.8-STABLE, or to any of the RELENG_4_8 (4.8-RELEASE-p2), RELENG_4_7 (4.7-RELEASE-p12), or RELENG_5_1 (5.1-RELEASE-p1) security branches dated after the respective correction dates (see original advisory).
Further details available in Customer Area

Original Advisory
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-03:09.signal.asc

Deep Links
Links available in Customer Area