Cisco Nexus 3000 and 9000 Series Switches Intermediate System-to-Intermediate System Denial of Service Vulnerability

SecurityVulns
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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.<br><br>
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.<br><br>
<strong>Note:</strong> The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device.<br><br>

Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.<br><br>
This advisory is available at the following link:<br><a href=”https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-n39k-isis-dos-JhJA8Rfx”>https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-n39k-isis-dos-JhJA8Rfx</a><br><br>

This advisory is part of the August 2025 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see <a href=”https://sec.cloudapps.cisco.com/security/center/viewErp.x?alertId=ERP-75667″ rel=”nofollow”>Cisco Event Response: August 2025 Semiannual Cisco FXOS and NX-OS Software Security Advisory Bundled Publication</a>.<br><br>

<br/>Security Impact Rating: High

<br/>CVE: CVE-2025-20241Cisco Security AdvisoryRead More