Vulnerability record · CVE-2026-20051 · published 25 February 2026
CVE-2026-20051: A vulnerability with the Ethernet VPN (EVPN) Layer 2 ingress packet processing of Cisco Nexus 3600 Platform Sw…
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.
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.
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
References
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Related vulnerabilities
Same products first, then exploited flaws of the same weakness class.
Source: NIST National Vulnerability Database (record CVE-2026-20051), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.
