A vulnerability in the IP version 6 (IPv6) processing code of Cisco IOS XR Software for Cisco CRS-3 Carrier Routing System could allow an unauthenticated, remote attacker to trigger an ASIC scan of the Network Processor Unit (NPU) and a reload of the line card processing an IPv6 packet.
The vulnerability is due to incorrect processing of an IPv6 packet carrying IPv6 extension headers that are valid but unlikely to be seen during normal operation. An attacker could exploit this vulnerability by sending such an IPv6 packet to an affected device that is configured to process IPv6 traffic. An exploit could allow the attacker to cause a reload of the line card, resulting in a DoS condition.
Cisco has confirmed the vulnerability in a security advisory and released software updates.
To exploit this vulnerability, an attacker may need to acquire additional information about the targeted device, such as whether the device has specific line cards installed and configured to process IPv6 traffic in addition to running an affected release of Cisco IOS XR Software. An attacker cannot exploit this vulnerability if these conditions are not met.
A successful exploit of this vulnerability could cause a widespread availability impact to systems that rely on an affected device for traffic forwarding.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.