CVE-2026-20051
Cisco Nexus 3600-R and 9500-R Series Switching Platforms Layer 2 Loop Denial of Service Vulnerability
Description
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 result in a denial of service (DoS) condition. This Layer 2 loop could oversubscribe the bandwidth on network interfaces, which would result in all data plane traffic being dropped. To exploit this vulnerability, the attacker must be Layer 2-adjacent to the affected device. Note: To stop active exploitation of this vulnerability, manual intervention is required to both stop the crafted traffic and flap all involved network interfaces. For additional assistance if a Layer 2 loop that is related to this vulnerability is suspected, contact the Cisco Technical Assistance Center (TAC) or the proper support provider.
Weakness: CWE-457
Affected products
| Vendor | Product | Category | Matched by |
|---|---|---|---|
| Cisco | Cisco NX-OS Software | Routing & Switching | cna-assigner |
Vendor-reported products (1)
- Cisco · Cisco NX-OS Software
Vendor advisory
cisco-sa-nxos-ether-dos-Kv8YNWZ4
Cisco Nexus 3600 and 9500-R Series Switching Platforms Layer 2 Loop Denial of Service Vulnerability
Cisco’s rating: High (advisory CVSS 7.4) · Published Feb 25, 2026
Bug ID: CSCwo94451
The vendor’s rating applies to the whole advisory and can differ from this CVE’s own CVSS severity. Where this comes from