From: Secunia Security Advisories (sec-advsecunia.com)
Date: Mon Feb 27 2006 - 09:32:04 CST

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TITLE:
Snort frag3 Preprocessor Packet Reassembly Vulnerability

SECUNIA ADVISORY ID:
SA18959

VERIFY ADVISORY:
http://secunia.com/advisories/18959/

CRITICAL:
Moderately critical

IMPACT:
Security Bypass

WHERE:
From remote

SOFTWARE:
Snort 2.4.x
http://secunia.com/product/5691/

DESCRIPTION:
siouxsie has reported a vulnerability in Snort, which potentially can
be exploited by malicious people to bypass certain security
restrictions.

The vulnerability is caused due to an error in the frag3 preprocessor
which causes snort to skip "ip_option_length" bytes from the end of
the IP options when reassembling a packet. This can potentially be
exploited to bypass signature detection via certain specially-crafted
fragmented packets.

The vulnerability has been reported in version 2.4.3. Other versions
may also be affected.

SOLUTION:
Filter potentially malicious fragmented IP packets with a firewall.

PROVIDED AND/OR DISCOVERED BY:
siouxsie

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