Cisco Adaptive Security Appliance Software contains a vulnerability that could allow an authenticated, remote attacker to cause a denial of service condition. Updates are available.
A vulnerability in the implementation of the rewriter module of the Cisco Adaptive Security Appliance (ASA) Clientless SSL VPN could allow an authenticated, remote attacker to cause a reload of the affected system.
The vulnerability is due to a race condition while accessing resources via the Common Internet File System (CIFS) protocol. An attacker could exploit this vulnerability by creating multiple Clientless SSL VPN sessions and trying to recreate the race condition.
Cisco has confirmed the vulnerability in a security notice and software updates are available.
At the time this alert was first published, Cisco ASA Software versions 8.4.6 and prior were affected. Later versions of Cisco ASA Software may also be affected.
To exploit the vulnerability, an attacker would need to authenticate to a targeted system to create multiple Clientless SSL VPN sessions. Typically, such devices reside on trusted, internal networks. This access requirement may reduce the likelihood of a successful attack.
Customers are advised to review the bug report in the Vendor Announcements section for a current list of affected versions.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
An authenticated, remote attacker could exploit this vulnerability to cause an affected system to reload, resulting in a denial of service (DoS) condition.
The vulnerability is in the rewriter module of the affected software while accessing resources via the CIFS protocol.
An authenticated, remote attacker could exploit this vulnerability by creating multiple Clientless SSL VPN sessions on a targeted device. If successful, a race condition could occur that an attacker could use to cause the device to reload, resulting in a DoS condition.
Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators are advised to allow only privileged users to access administration or management 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 e-mail at firstname.lastname@example.org for assistance.
The urgency and severity ratings of this alert are not tailored to individual users; users may value alerts differently based upon their network configurations and circumstances. THE ALERT, AND INFORMATION CONTAINED THEREIN, ARE PROVIDED ON AN "AS IS" BASIS AND DO NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE ALERT, AND INFORMATION CONTAINED THEREIN, OR MATERIALS LINKED FROM THE ALERT, IS AT YOUR OWN RISK. INFORMATION IN THIS ALERT AND ANY RELATED COMMUNICATIONS IS BASED ON OUR KNOWLEDGE AT THE TIME OF PUBLICATION AND IS SUBJECT TO CHANGE WITHOUT NOTICE. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE ALERTS AT ANY TIME.