Vulnerability Description
A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) multi-instance routing feature of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause the IS-IS process to restart unexpectedly. This vulnerability is due to insufficient input validation of ingress IS-IS packets. An attacker could exploit this vulnerability by sending crafted IS-IS packets to an affected device after forming an adjacency. A successful exploit could allow the attacker to cause the IS-IS process to restart unexpectedly, resulting in a temporary loss of connectivity to advertised networks and a denial of service (DoS) condition. Note: The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device and must have formed an adjacency.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Cisco | Ios Xr | >= 7.8.0, < 25.2.2 |
Related Weaknesses (CWE)
References
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/ciMitigationVendor Advisory
FAQ
What is CVE-2026-20074?
CVE-2026-20074 is a vulnerability with a CVSS score of 7.4 (HIGH). A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) multi-instance routing feature of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause the IS-IS p...
How severe is CVE-2026-20074?
CVE-2026-20074 has been rated HIGH with a CVSS base score of 7.4/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-20074?
Check the references section above for vendor advisories and patch information. Affected products include: Cisco Ios Xr.