Cisco Security Advisory
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AV:R/AC:L/Au:NR/C:N/I:N/A:P/B:N/E:U/RL:O/RC:C
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Cisco Intrusion Prevention System versions prior to 5.1(2) contain a vulnerability that could allow an unauthenticated, remote attacker to bypass security scanning.
This vulnerability is due to a failure to properly handle fragmented packets. An unauthenticated, remote attacker can exploit this vulnerability by sending network requests in such a way that IPS detection rules are not triggered. This can allow an attacker to circumvent IPS scanning and protection, allowing the attacker to potentially pass malicious traffic on secure networks.
Cisco has confirmed this vulnerability in a security advisory and released updated software that corrects it.
Attackers may attempt to exploit this vulnerability to carry out attacks against secondary targets. Because the attacker can pass malicious traffic without scanning, IPS devices would be unable to mitigate such attacks. It is likely that this type of vulnerability will be utilized in targeted attacks where the attacker has intimate knowledge of the network topology.
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Cisco has released a security advisory regarding Cisco bug IDs CSCse17206 (for registered users) and CSCsf12379 (for registered users) at the following link: Cisco-SA-20060920-ips
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Administrators are advised to apply the appropriate software updates.
Administrators may consider employing secondary filtering devices until updates can be applied.
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Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via e-mail at tac@cisco.com.
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The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Show LessVersion Description Section Status Date 1.0 Initial Release NA Final 2006-Sep-20
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