TITLE:
OpenBSD TCP Retransmission Timeout Calculation Denial of Service

SECUNIA ADVISORY ID:
SA13819

VERIFY ADVISORY:
http://secunia.com/advisories/13819/

CRITICAL:
Not critical

IMPACT:
DoS

WHERE:
Local system

OPERATING SYSTEM:
OpenBSD 3.x
http://secunia.com/product/100/

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

The vulnerability is caused due to an error in the TCP stack when
calculating TCP retransmission timeouts. This can be exploited to
crash the system by sending some specially crafted packets with
specific values in the TCP timestamp option.

SOLUTION:
Apply patches.

OpenBSD 3.6:
ftp://ftp.openbsd.org/pub/OpenBSD/patches/3.6/common/010_rtt.patch

OpenBSD 3.5:
ftp://ftp.openbsd.org/pub/OpenBSD/patches/3.5/common/027_rtt.patch

PROVIDED AND/OR DISCOVERED BY:
Reported by vendor.

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