CVE-2026-20074

Published Mar 11, 2026

Last updated 14 days ago

Overview

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.  
Source
psirt@cisco.com
NVD status
Analyzed
Products
ios_xr

Risk scores

CVSS 3.1

Type
Secondary
Base score
7.4
Impact score
4
Exploitability score
2.8
Vector string
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Severity
HIGH

Weaknesses

psirt@cisco.com
CWE-1287

Social media

Hype score
Not currently trending

Configurations