Cisco NX-OS Control Plane DoS Vulnerability (CVE-2026-20173) Security Advisory

Vulnerability Overview Vulnerability Name: Cisco NX-OS Software Control Plane Denial of Service Vulnerability Vulnerability ID: cisco-sa-nxos-nscpds-SnderkC7 CVE Identifier: CVE-2026-20173 CVSS Score: Base 5.9 Severity: Medium Publication Date: October 7, 2026, 16:00 GMT Version: 1.0 Status: Final Description: This vulnerability allows an unauthenticated, remote attacker to cause a denial of service (DoS) condition by exhausting system resources. This vulnerability exists because rate limiting is not correctly applied to certain protocols. An attacker can exploit this vulnerability by sending a large number of UDP or TCP connections to data plane interfaces, causing instability in various routing and control plane protocols, which leads to a DoS condition. This DoS condition does not clear automatically after high traffic subsides. Affected Products Affected Products: Nexus 3000 Series Switches (CSCws61989) Nexus 7000 Series Switches (CSCws28932) Nexus 9000 Series Switches in standalone NX-OS mode (CSCws61989) Unaffected Products: Firepower 1000 Series Firepower 2100 Series Firepower 4100 Series Firepower 9300 Security Appliances MDS 9000 Series Multilayer Switches Nexus 9000 Series Fabric Switches in ACI mode Secure Firewall 200 Series Secure Firewall 1200 Series Secure Firewall 3100 Series Secure Firewall 4200 Series Secure Firewall 6100 Series UCS 6300 Series Fabric Interconnects UCS 6400 Series Fabric Interconnects UCS 6500 Series Fabric Interconnects UCS 6600 Series Fabric Interconnects UCS X-Series Direct Fabric Interconnect 9108 100G Remediation Workaround: None Fixed Software: Cisco strongly recommends that customers upgrade to the following fixed software versions: - Use the Cisco Software Checker tool to determine affected products and recommended software versions. - Visit the Cisco Software Checker page and follow the instructions. - Select the appropriate platform and software version, enter the release version number, and click Check. Additional Resources: Cisco MDS Series Switches Cisco Nexus 3000 Series Switches Cisco Nexus 7000 Series Switches Cisco Nexus 9000 Series Switches Cisco Nexus 9000 Series ACI-Mode Switches Source: Thanks to Naresh Chamdal of CGI UK for reporting this vulnerability. URL: Cisco Security Advisory Revision History: Version 1.0: Initial public release, status Final, date October 7, 2026. Legal Disclaimer: Contains details regarding software download and technical support, as well as disclaimers and legal terms.

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Cisco NX-OS Control Plane DoS Vulnerability (CVE-2026-20173) Security Advisory

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