CVE-2023-20227

Vulnerability

The vulnerability resides in the Layer 2 Tunneling Protocol (L2TP) feature of Cisco IOS XE Software. It is caused by improper handling of certain L2TP packets. An unauthenticated, remote attacker can trigger a denial of service (DoS) condition by sending crafted L2TP packets to an affected device. Only traffic directed to the affected system can be used to exploit this vulnerability. The advisory does not list specific affected versions, but the fix is included in software updates released by Cisco.

Exploitation

An attacker needs network reachability to the target device and can send specially crafted L2TP packets. No authentication or user interaction is required. The attack is limited to traffic directed at the affected system, meaning the attacker must be able to send packets to the device's IP address on the L2TP port.

Impact

Successful exploitation causes the affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. The impact is a temporary loss of network services until the device recovers from the reload.

Mitigation

Cisco has released free software updates to address this vulnerability [1]. Customers with service contracts can obtain fixes through their usual update channels. Those without service contracts should contact the Cisco Technical Assistance Center (TAC) for assistance. No workarounds are mentioned in the reference.