Quick answers
- Is CVE-2026-76505 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-76505 being exploited in the wild.
- How severe is CVE-2026-76505?
- High severity, with a CVSS score of 7.5, published 21 October 2026.
- Which products and versions are affected?
- Cisco ASR 9000 Series With Lightspeed or Lightspeed-Plus line cards running vulnerable IOS XR releases; Cisco ASR 9900 Series With Lightspeed or Lightspeed-Plus line cards running vulnerable IOS XR releases; Cisco ASR 9902 Running vulnerable IOS XR releases; Cisco ASR 9903 Running vulnerable IOS XR releases; and 1 more.
- Is there a fix for CVE-2026-76505?
- No fixed version is recorded yet. Configure ingress infrastructure access control lists (iACL) on edge or external interfaces to filter and drop UDP port 1701 traffic destined for local router addresses (infrastructure address space) while permitting legitimate transit traffic.</anigation> <parameter name="timeline">[ { "kind": "disclosed", "at": "2026-10-21" } ] If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-76505 attacked?
- It is attacked over the network, in a network appliance.
- Am I affected by CVE-2026-76505?
- Check whether you run Cisco ASR 9000 Series, Cisco ASR 9900 Series, Cisco ASR 9902 or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
Configure ingress infrastructure access control lists (iACL) on edge or external interfaces to filter and drop UDP port 1701 traffic destined for local router addresses (infrastructure address space) while permitting legitimate transit traffic.</anigation> <parameter name="timeline">[ { "kind": "disclosed", "at": "2026-10-21" } ]
Technical details
The vulnerability exists in the IPv4 packet-processing path within IOS XR Software on affected ASR routers with Lightspeed or Lightspeed-Plus line cards. An unauthenticated remote attacker can send crafted IPv4 packets destined for the router itself (for-us traffic) to trigger network processor errors. The vulnerability is triggered only in for-us traffic handling; transit traffic and IPv6 are unaffected.
Affected products
- Cisco IOS XR Vulnerable releases on ASR 9000, 9900, 9902, 9903 Series with Lightspeed or Lightspeed-Plus line cards
- Cisco ASR 9000 Series With Lightspeed or Lightspeed-Plus line cards running vulnerable IOS XR releases
- Cisco ASR 9900 Series With Lightspeed or Lightspeed-Plus line cards running vulnerable IOS XR releases
- Cisco ASR 9902 Running vulnerable IOS XR releases
- Cisco ASR 9903 Running vulnerable IOS XR releases