Cisco Security Advisory
Cisco ASA VPN Denial of Service Vulnerability
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AV:N/AC:H/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
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A vulnerability in the VPN authentication code that handles parsing of the username from the certificate on the Cisco ASA firewall could allow an unauthenticated, remote attacker to cause a reload of the affected device.
The vulnerability is due to parallel processing of a large number of Internet Key Exchange (IKE) requests for which username-from-cert is configured. An attacker could exploit this vulnerability by sending a large number of IKE requests when the affected device is configured with the username-from-cert command. An exploit could allow the attacker to cause a reload of the affected device, leading to a denial of service (DoS) condition.
Cisco has confirmed the vulnerability in a security notice and released software updates.
To exploit this vulnerability, an attacker must send a large number of IKE requests to a targeted device, which may reside on trusted, internal networks that the attacker would likely need to access. This access requirement decreases the likelihood of a successful exploit. In addition, the targeted device must be configured with the username-from-cert command.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
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Customers are advised to consult Cisco bug ID CSCua91108 for a complete list of affected product versions.
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Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators are advised to monitor affected systems.
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Cisco customers with active contracts should contact their Cisco support team for assistance in upgrading to a software version that includes fixes for this vulnerability. Cisco customers without contracts may contact the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via email at tac@cisco.com for assistance.
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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 2013-Oct-22
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