Is CVE-2026-20074 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-20074 being exploited in the wild.

How severe is CVE-2026-20074?

High severity, with a CVSS score of 7.4, published 11 March 2026.

Which products and versions are affected?

Cisco IOS XR Software 7.8.0 through 25.2.1, 25.3.0.

Is there a fix for CVE-2026-20074?

A patch was published on 2026-03-11: Fixed versions 25.2.2 and 25.3.1 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-20074 attacked?

It is attacked from the adjacent network, in an operating system.

Am I affected by CVE-2026-20074?

Check whether you run Cisco IOS XR Software 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.

CVE-2026-20074: Cisco IOS XR Software DoS in IS-IS Multi-Instance Routing

CVE-2026-20074 · Severity: high · CVSS 7.4 · Published 2026-03-11

A vulnerability in Cisco's networking software for service provider routers could allow an attacker on the same local network to crash the routing process. This affects the IS-IS protocol, which is used to direct traffic across large networks. If exploited, the router would temporarily lose its ability to communicate with other parts of the network, leading to a service outage and potential disruption of customer internet or data services.

Technologies: Cisco IOS XR Software. Vendors: Cisco.

Quick answers

Is CVE-2026-20074 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-20074 being exploited in the wild.
How severe is CVE-2026-20074?: High severity, with a CVSS score of 7.4, published 11 March 2026.
Which products and versions are affected?: Cisco IOS XR Software 7.8.0 through 25.2.1, 25.3.0.
Is there a fix for CVE-2026-20074?: A patch was published on 2026-03-11: Fixed versions 25.2.2 and 25.3.1 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-20074 attacked?: It is attacked from the adjacent network, in an operating system.
Am I affected by CVE-2026-20074?: Check whether you run Cisco IOS XR Software 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.

Technical details

The vulnerability exists in the IS-IS multi-instance routing feature of Cisco IOS XR Software due to improper input validation of ingress IS-IS packets (CWE-1287). An unauthenticated attacker who is Layer 2-adjacent to the target device can exploit this by first forming a routing adjacency and then sending specifically crafted IS-IS packets. A successful exploit triggers an unexpected restart of the IS-IS process, causing a temporary loss of routing information and connectivity to advertised networks. The vulnerability specifically affects devices with 'instance-id' configured under the IS-IS router process. Cisco has released software updates and suggests configuring IS-IS area authentication as a mitigation to prevent unauthorized adjacency formation.

Affected products

Cisco IOS XR Software 7.8.0 through 25.2.1, 25.3.0

Timeline

2026-03-11: advisory: Initial public release by Cisco
2026-03-11: patched: Fixed versions 25.2.2 and 25.3.1 released

References

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK

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