CVE-2026-20074: high-severity vulnerability in Cisco IOS XR Software
Cisco IOS XR Software Multi-Instance Intermediate System-to-Intermediate System Denial of Service Vulnerability
Published
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.4epss 0.2%
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:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Affected products
Cisco · Cisco IOS XR SoftwareRelated CVEs — Cisco IOS XR Software
In the same product, most dangerous first.
CVE-2020-3118HIGHCisco IOS XR Software Cisco Discovery Protocol Format String VulnerabilityEPSS 11.7%KEVCVE-2022-20821MEDIUMCisco IOS XR Software Health Check Open Port VulnerabilityEPSS 11.5%KEVCVE-2020-3566HIGHCisco IOS XR Software DVMRP Memory Exhaustion VulnerabilityEPSS 3.7%KEVCVE-2020-3569HIGHCisco IOS XR Software DVMRP Memory Exhaustion VulnerabilitiesEPSS 3.3%KEVCVE-2025-20363CRITICALCVE-2025-20363EPSS 6.9%CVE-2020-3284HIGHCisco IOS XR Software Enhanced Preboot eXecution Environment Unsigned Code Execution VulnerabilityEPSS 2.9%