Cisco NX-OS Software Control Plane Denial of Service Vulnerability

Description

A vulnerability in Cisco NX-OS Software could allow an unauthenticated, remote attacker to exhaust system resources, causing a denial of service (DoS) condition. This vulnerability exists because rate limiting was improperly applied to some protocols. An attacker could exploit this vulnerability by sending a high rate of UDP or TCP connections to a data plane interface on an affected device. A successful exploit could allow the attacker to cause instability to various routing and control plane protocols through some packet loss and temporary disruptions, causing a DoS condition. This DoS condition will clear without manual intervention soon after the high rate of traffic is stopped. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is available at the following link: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-nscpdos-SnderkC7 This advisory is part of a group of advisories. For a complete list of the advisories and links to them, see Cisco Advance Notification for Publication of October 7, 2026, Security Advisories . For further documentation of improvements and fixes in Cisco NX-OS Software, see Cisco NX-OS Software Security Hardening Release: October 2026 . Security Impact Rating: Medium CVE: CVE-2026-20173

What to do

Install the fixed versions listed in the official advisory. If you cannot update right away, apply the workarounds or mitigations it describes and limit access to the affected service.

Details

Vendor

Cisco

Product

Cisco NX-OS

CVE

CVE-2026-20173

Affected versions

Cisco NX-OS Software 8.2: 12 versions, from 8.2(5) to 8.2(11)
Cisco NX-OS Software 7.3: 15 versions, from 7.3(5)D1(1) to 7.3(9)D1(1)
Cisco NX-OS Software 8.4: 14 versions, from 8.4(2) to 8.4(12)
Cisco NX-OS Software 9.2: 7 versions, from 9.2(3) to 9.2(2)
Cisco NX-OS Software 9.3: 21 versions, from 9.3(2) to 9.3(17)
Cisco NX-OS Software 8.1: 8.1(1); 8.1(2); 8.1(2a)
Cisco NX-OS Software 8.3: 8.3(2); 8.3(1)
Cisco NX-OS Software 10.3: 19 versions, from 10.3(1) to 10.3(8)
Cisco NX-OS Software 10.4: 8 versions, from 10.4(1) to 10.4(7)
Cisco NX-OS Software 10.5: 10 versions, from 10.5(1) to 10.5(5) (from the advisory and NVD; check the exact builds in the official advisory)

CVSS score

5.8

Actively exploited

Not known at this time

Source

Cisco PSIRT – original advisory

Published

October 7, 2026

The description and the recommended action are quoted from the public advisory (the action is our generic advice); severity, exploitation status and affected versions are compiled automatically from public sources and may contain errors. The vendor's original advisory prevails: check it before taking action. This information is provided without warranty and does not replace a professional assessment.