TITLE:
FreeBSD "pf" IP Fragment Denial of Service Vulnerability

SECUNIA ADVISORY ID:
SA18609

VERIFY ADVISORY:
http://secunia.com/advisories/18609/

CRITICAL:
Moderately critical

IMPACT:
DoS

WHERE:
>From remote

OPERATING SYSTEM:
FreeBSD 6.x
http://secunia.com/product/6778/
FreeBSD 5.x
http://secunia.com/product/1132/

DESCRIPTION:
A vulnerability has been reported in FreeBSD, which can be exploited
by malicious people to cause a DoS (Denial of Service).

The vulnerability is caused due to an error in the "pf" Internet
Protocol packet-filter fragment cache when handling IP fragments.
This can be exploited to crash the system by sending a
specially-crafted sequence of IP packet fragments to the packet
filter.

Successful exploitation requires that "pf" is used with a ruleset
containing "scrub fragment crop" or "scrub fragment drop-ovl" rules.

The vulnerability has been reported in version 5.3, 5.4, and 6.0.

SOLUTION:
Update FreeBSD or apply patch.

Fixed versions:
2006-01-25 10:00:59 UTC (RELENG_6, 6.0-STABLE)
2006-01-25 10:01:26 UTC (RELENG_6_0, 6.0-RELEASE-p4)
2006-01-25 10:01:47 UTC (RELENG_5, 5.4-STABLE)
2006-01-25 10:02:07 UTC (RELENG_5_4, 5.4-RELEASE-p10)
2006-01-25 10:02:27 UTC (RELENG_5_3, 5.3-RELEASE-p25)

Patch for FreeBSD 5.3, 5.4, and 6.0:
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:07/pf.patch
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:07/pf.patch.asc

PROVIDED AND/OR DISCOVERED BY:
The vendor credits Jakob Schlyter and Daniel Hartmeier.

ORIGINAL ADVISORY:
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:07.pf.asc

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