Cisco Adaptive Security Appliance Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available.
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.
At the time this alert was first published, Cisco ASA Software versions 8.4(4.5) and prior were vulnerable. Later releases of Cisco ASA may also be vulnerable.
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.
Cisco has released a security notice at the following link: CVE-2013-5544
Customers are advised to consult Cisco bug ID CSCua91108 for a complete list of affected product versions.
An unauthenticated, remote attacker could exploit this vulnerability to cause an affected device to reload, resulting in a DoS condition.
The vulnerability is due to parallel processing of a large number of IKE requests for which username-from-cert is configured.
An unauthenticated, remote 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 DoS condition.
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.
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 email@example.com for assistance.
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