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Category:   Application (Security)  >   Cisco Snort Vendors:
Snort Rule Matching Complexity Lets Remote Users Deny Service via Backtracking Attacks
SecurityTracker Alert ID:  1017508
SecurityTracker URL:
CVE Reference:   CVE-2006-6931   (Links to External Site)
Updated:  May 19 2008
Original Entry Date:  Jan 12 2007
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  Exploit Included:  Yes  
Version(s): prior to 2.6.1
Description:   A vulnerability was reported in Snort. A remote user can cause denial of service conditions.

A remote user can send specially crafted packets that backtrack to invoke all possible string or regular expression matchs contained in a Snort filter. Such a "worst case" backtracking attack can cause the target system to take an excessive amount of time to test the rule against the packet. As a result, the system may be unable to keep up with incoming packets and a remote user can evade detection.

Randy Smith, Christian Estan, and Somesh Jha of the University of Wisconsin-Madison discovered this vulnerability.

The original advisory is available at:

Impact:   A remote user can cause denial of service conditions, which may allow the remote user to evade detection.
Solution:   The vendor has issued a fixed version (2.6.1).

The Snort advisory is available at:

Vendor URL: (Links to External Site)
Cause:   State error
Underlying OS:  Linux (Any), UNIX (Any), Windows (Any)

Message History:   None.

 Source Message Contents

[Original Message Not Available for Viewing]

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