CVE-2026-76505: Cisco IOS XR Software for ASR 9000 Series Routers IPv4 Unicast Packets Denial of Service Vulnerability
A vulnerability in the IPv4 packet processing functionality of Cisco IOS XR Software that affects Cisco ASR 9000 and 9900 Series Aggregation Services Routers as well as Cisco ASR 9902 and 9903 Compact High-Performance Routers could allow an unauthenticated, remote attacker to cause network processor (NP) errors, resulting in a line card reset or shutdown and a denial of service (DoS) condition. This vulnerability is due to the incorrect handling of crafted IPv4 packets that are received on an affected line card interface and processed as for-us traffic. The issue can result in an NP reset, causing traffic loss on the affected line card while it recovers. Under repeated reset conditions, the network processor may enter a persistent shutdown state, in which case an explicit line card reload may be required to restore traffic. The vulnerability is within the IPv4 packet-processing path. Transit IPv4 traffic does not trigger this issue and IPv6 traffic cannot trigger it.
Affected Software
Event History
Frequently Asked Questions
Which devices and traffic paths are exposed?
The issue affects Cisco ASR 9000 and 9900 Series Aggregation Services Routers and Cisco ASR 9902 and 9903 Compact High-Performance Routers running Cisco IOS XR Software. Only crafted IPv4 packets received on an affected line card interface and processed as for-us traffic can trigger it; transit IPv4 and IPv6 traffic do not.
Does exploitation require authentication or user interaction?
No. An unauthenticated remote attacker can trigger the condition by sending crafted IPv4 packets to an affected line card interface, provided the packets are processed as for-us traffic.
What operational impact should responders expect?
Exploitation can cause a network processor reset and traffic loss on the affected line card while it recovers. Repeated resets can place the network processor into a persistent shutdown state, requiring an explicit line card reload to restore traffic.