Cisco has released a blog post and released bug reports with additional information to address reports of the TCP split handshake connection vulnerability in Cisco products.
Description
Researchers from NSS Labs have announced that the Cisco ASA Adaptive Security Appliance (along with products from other firewall vendors) is affected by the TCP Split Handshake weakness initially discovered by BreakingPoint Systems. Cisco engineers have been unable to confirm the vulnerability in any Cisco products.
The weakness could allow an attacker to establish connections through targeted devices even where connections may otherwise be disabled in access control lists (ACLs) or filter rules. TCP connections using a split handshake to establish a session could also bypass filtering for malicious activity because filtering devices may be unable to detect communications within connections established out of the norm.
As a matter of policy, Cisco takes security vulnerabilities very seriously and we continue to take active measures to safeguard the security and reliability of our equipment. Cisco has been working with NSS Labs on the TCP split handshake spoof since early this year. In this time, Cisco PSIRT has been unable to confirm any new security vulnerabilities in Cisco products, and have demonstrated the Cisco ASA protects against this attack. Cisco PSIRT continues to work with NSS Labs, and will follow our well-established disclosure process should any new information come to light. PSIRT will disclose any security vulnerabilities discovered in compliance with the Cisco security vulnerability policy: Cisco Security Vulnerability Policy
Cisco Intrusion Prevention System (IPS) - CSCth67416
Alert History
Version 1, April 12, 2011, 2:39 PM: Multiple vendor firewall devices may contain a weakness that could allow attackers to evade filtering or bypass security restrictions.
The security vulnerability applies to the following combinations of products.
Primary Products:
IntelliShield
Security Activity Bulletin
Original Release Base
Associated Products:
N/A
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