Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.†
The vulnerability is due to a error in the implementation of the Internet Key Exchange (IKE) protocol during certificate-based authentication.† An unauthenticated, remote attacker could exploit this vulnerability by making crafted requests to the system.† These requests could cause the system to expend resources that are required for the creation of IPsec sessions.† An exploit could cause a DoS condition on IPsec services, which could prevent the creation of new IPsec sessions.
Cisco has confirmed this vulnerability and released updated software.
Indicators of Compromise
Cisco has published a list of affected Cisco IOS Software releases in the security advisory.† The Vendor Announcements section of this alert contains a link to the advisory.
The vulnerability is due to an error that may occur when the IKE protocol is configured for certificate-based authentication.† An unauthenticated, remote attacker could exploit this vulnerability by making crafted requests to the system.† The requests could cause the system to expend all available Phase 1 security associations (SAs) that are used to create new IPsec sessions.† An exploit could result in a DoS condition on IPsec.† No new IPsec sessions can be created until Phase 1 SAs have been de-allocated.†
The vulnerability only exists on systems that are configured to use the IKE protocol and certificate-based authentication, which are enabled by default if IPsec has been enabled.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
Administrators are advised to apply the appropriate updates.
Administrators are advised to monitor affected systems for signs of exploitation.† The Cisco Security Advisory provides additional details on system monitoring.
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-amb-20090923-ipsec
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.
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.