Cisco has released an updated security advisory to identify additional software versions affected by the Cisco Wireless LAN Controller denial of service vulnerability.
Cisco Wireless LAN Controller (WLC) software contains a vulnerability that could allow an authenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability is due to the way the Cisco WLC handles malicious network traffic that is destined for the device. An authenticated, remote attacker who can send a series of malicious packets to the Cisco WLC could cause the device to reload, resulting in a DoS condition.
Cisco has confirmed this vulnerability in a security advisory and released updated software.
Devices running the following versions of Cisco Wireless LAN Controller software are vulnerable:
Versions prior to 188.8.131.52
Versions prior to 184.108.40.206M
All 5.0 versions
All 5.1 versions
Versions prior to 220.127.116.11
Versions prior to 18.104.22.168
A potential attacker would likely need access to internal or private networks and would need to authenticate to the vulnerable device. These requirements could reduce the potential for an attack because an attacker who does not already have this level of access would need to gain network access and compromise an active account. A three-way handshake is also required for successful exploitation.
WebAuth and guest access are not affected by this vulnerability.
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 trigger this vulnerability, causing the Cisco WLC to reload. A device reload will result in a DoS condition. This DoS condition could be temporary. However, if the exploit is repeated, a sustained DoS condition could result.
An attacker can exploit this vulnerability by sending a series of malformed HTTP packets that contain invalid arguments to the embedded web server (emweb). The packets must be destined for the vulnerable device; transit traffic will not trigger the exploit.
An authenticated, remote attacker who has wired or wireless access to the vulnerable device could cause a DoS condition. This condition could be temporary because the device will automatically reload. However, if the attack is repeated, the DoS condition could be sustained. Either result will prevent user access to the device, disrupting operations.
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 implement an intrusion prevention system (IPS) or intrusion detection system (IDS) to help detect and prevent attacks that attempt to exploit this vulnerability.
Administrators are advised to monitor affected systems.
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-20100908-wlc
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 email@example.com.
Version 1, September 8, 2010, 12:13 PM: Cisco Wireless LAN Controller software contains a vulnerability that could allow an authenticated, remote attacker to cause a denial of service condition. Updates are available.
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.