CVE-2025-20241: Cisco NX-OS Software

High severity, CVSS 7.4. EPSS: 0.3% chance of exploitation in the next 30 days.

A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) feature of Cisco NX-OS Software for Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, adjacent attacker to cause the IS-IS process to unexpectedly restart, which could cause an affected device to reload. This vulnerability is due to insufficient input validation when parsing an ingress IS-IS packet. An attacker could exploit this vulnerability by sending a crafted IS-IS packet to an affected device. A successful exploit could allow the attacker to cause the unexpected restart of the IS-IS process, which could cause the affected device to reload, resulting in 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.

Affected products

• Cisco Cisco NX-OS Software: version 9.2(3) only; version 7.0(3)I5(2) only; version 6.0(2)A8(7a) only; version 7.0(3)I4(5) only; version 7.0(3)I4(6) only; version 7.0(3)I4(3) only; …

Published 2025-08-27. Last modified 2026-06-17.