CVE-2026-76505
Cisco IOS XR Software for ASR 9000 Series Routers IPv4 Unicast Packets Denial of Service Vulnerability
Description
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.
Weakness: CWE-20
Affected products
| Vendor | Product | Category | Matched by |
|---|---|---|---|
| Cisco | Cisco IOS XR Software | Routing & Switching | cna-assigner |
Vendor-reported products (1)
- Cisco · Cisco IOS XR Software
Vendor advisory
Cisco IOS XR Software for ASR 9000 Series Routers IPv4 Unicast Packets Denial of Service Vulnerability
Cisco’s rating: High (advisory CVSS 7.5) · Published Oct 21, 2026
Bug ID: CSCwn39554
The vendor’s rating applies to the whole advisory and can differ from this CVE’s own CVSS severity. Where this comes from