Cisco has re-released the security advisory for the Cisco IOS XR Software Border Gateway Protocol attribute processing denial of service vulnerability to include updated software versions.
Cisco IOS XR Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability is due to errors in processing Border Gateway Protocol (BGP) route updates that contain unrecognized attributes. An unauthenticated, remote attacker could exploit this vulnerability by sending malicious BGP routes to a targeted device. When processed, the route updates could cause the device to distribute corrupted routes, causing devices that accept the corrupted routes to close BGP sessions, resulting in a DoS condition.
Cisco confirmed this vulnerability in a security update and software updates are available.
Cisco IOS XR Software versions 3.9.1 and prior are affected.
To exploit this vulnerability, an attacker would have to send malicious BGP route updates to the targeted device. Routers typically accept BGP route updates only from authorized BGP neighbors. An attacker must send malicious routes to a targeted device from an approved peer or otherwise spoof the source of updates to make the targeted device accept a provided route update. These access requirements greatly reduce the potential for exploitation.
The vulnerability was discovered during the implementation of an experimental BGP route update. The event is documented in IntelliShield Alert 21265.
An unauthenticated, remote attacker could exploit this vulnerability to cause a targeted device to close established BGP sessions, resulting in a DoS condition.
The vulnerability is due to errors in processing BGP route updates that contain unrecognized attributes. When processing the update, the Cisco IOS XR Software may corrupt the attribute before passing the route update to other peers. As a result, BGP neighbors may reset an established BGP session.
An unauthenticated, remote attacker could exploit this vulnerability by sending a malicious route update to the targeted device. The attacker must send the route update from an authorized BGP neighbor, or otherwise spoof the source of the update, to force the targeted device to accept and process the update. When processed, the route update may trigger the distribution of corrupted updates, resulting in a DoS condition.
Administrators are advised to apply the appropriate updates.
Administrators are advised to monitor affected systems for signs of exploitation.
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.
Version 1, Aug 27, 2010, 8:01 PM: Cisco IOS XR Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are not available.
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