High [CVE-2026-20051] Cisco Nexus 3600 and 9500-R Series Switching Platforms Layer 2 Loop Denial of Service Vulnerability
This high-severity Cisco advisory covers CVE-2026-20051 affecting Cisco NX-OS Software 9.2(1), Cisco NX-OS Software 9.2(2), Cisco NX-OS Software 9.2(2t).
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Summary
A vulnerability with the Ethernet VPN (EVPN) Layer 2 ingress packet processing of Cisco Nexus 3600 Platform Switches and Cisco Nexus 9500-R Series Switching Platforms could allow an unauthenticated, adjacent attacker to trigger a Layer 2 traffic loop. This vulnerability is due to a logic error when processing a crafted Layer 2 ingress frame.
An attacker could exploit this vulnerability by sending a stream of crafted Ethernet frames through the targeted device. A successful exploit could allow the attacker to cause a Layer 2 Virtual eXtensible LAN (VxLAN) traffic loop, which, in turn, could …
Affected products named by the advisory: Cisco NX-OS Software 9.2(1); Cisco NX-OS Software 9.2(2); Cisco NX-OS Software 9.2(2t); Cisco NX-OS Software 9.2(3); and 4 more.
- Scope: This vulnerability affects only the following Cisco Nexus 3600 and 9500-R Switching Platform product identifiers (PIDs) if they are running a vulnerable release of Cisco NX-OS Software and have EVPN configured:
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
Mitigation checklist
- There are no workarounds that address this vulnerability.
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
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