TITLE:
FreeBSD SACK Handling Denial of Service

SECUNIA ADVISORY ID:
SA18696

VERIFY ADVISORY:
http://secunia.com/advisories/18696/

CRITICAL:
Moderately critical

IMPACT:
DoS

WHERE:
>From remote

OPERATING SYSTEM:
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 SACK (Selective
ACKnowledgement) handling and may result in an infinite loop when not
enough memory is available to handle an incoming SACK. This can be
exploited by opening up a TCP connection to a vulnerable system and
sending a specially crafted series of TCP packets.

Successful exploitation causes the TCP/IP stack to enter an infinite
loop.

SOLUTION:
Update FreeBSD or apply patch.

Fixed versions:
2006-01-24 01:16:18 UTC (RELENG_5, 5.4-STABLE)
2006-02-01 19:43:10 UTC (RELENG_5_4, 5.4-RELEASE-p11)
2006-02-01 19:43:36 UTC (RELENG_5_3, 5.3-RELEASE-p26)

Patch for FreeBSD 5.3 and 5.4:
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:08/sack.patch
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:08/sack.patch.asc

PROVIDED AND/OR DISCOVERED BY:
The vendor credits Scott Wood.

ORIGINAL ADVISORY:
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:08.sack.asc

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Please Note:
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Secunia NEVER sends attached files with advisories.
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use those supplied by the vendor.

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