Cisco Firewall Services Module, PIX Security Appliance, and ASA Security Appliance contain a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability exists due to an error when handling SIP messages. An unauthenticated, remote attacker could exploit this vulnerability by sending a malformed SIP message to an affected device. This action could cause the affected device to reload, resulting in a temporary DoS condition. Repeated attacks can result in a persistent DoS condition.
Cisco has confirmed this vulnerability with a security advisory and released updated software.
Successful exploitation allows the attacker to cause the affected device to reload, which could be considered a temporary DoS condition. Repeated attacks could result in a persistent denial of service condition.
A system is only vulnerable if deep packet inspection of SIP messages is enabled. This is handled by the fixup command in FWSM 2.x and ASA/PIX 6.x, and is enabled for SIP packets by default in these versions. It is handled by the inspect command in both FWSM 3.x and ASA/PIX 7.x. The inspect command is enabled by default in FWSM 3.x, and disabled by default in ASA/PIX 7.x.
Cisco has re-released a security advisory to address Cisco bug ID CSCsg80915 in the Cisco Firewall Services Module at the following link: cisco-sa-20070214-fwsm
Cisco has released a security advisory to address Cisco bug IDs CSCse27708 and CSCsd97077 in Cisco PIX and ASA appliances at the following link: cisco-sa-20070214-pix
US-CERT has released a vulnerability note at the following link: VU#430969
Systems running the following versions of Cisco Firewall Services Module are vulnerable:
Cisco Firewall Services Module prior to 2.3(4.12)
Cisco Firewall Services Module prior to 3.1(3.24)
Cisco PIX 500 Series Security Appliances and Cisco ASA 5500 Series Adaptive Security Appliances are vulnerable if they are using the following software releases:
Versions 6.0 prior to 6.3(5.115)
Versions 7.0 prior to 7.0(5.2)
Versions 7.1 prior to 7.1(2.5)
Products Confirmed Not VulnerableNo other Cisco products are currently known to be affected by these vulnerabilities.
Administrators are advised to apply the appropriate patch.
Administrators are advised to restrict access to affected systems.
Administrators may consider disabling deep packet inspection of SIP messages. This may impact devices that are terminating SIP sessions, as some malicious packets that may otherwise have been detected may be allowed to pass through.
Administrators of 3.x FWSM systems or 7.x ASA/PIX devices are advised to disallow traffic from untrusted hosts. However, since SIP is a UDP-based protocol, IP source address spoofing could be used to bypass IP-based ACLs.
The Cisco Applied Intelligence team has created the following companion document to guide administrators in identifying and mitigating attempts to exploit this vulnerability prior to applying updated software: cisco-air-20070214-firewall
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 firstname.lastname@example.org.
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.
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.
Version Description Section Status Date 1.0 Initial Release NA Final 2007-Feb-14
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