What is the CVSS score of CVE-2026-20051?

CVE-2026-20051 has a CVSS 3.1 base score of 7.4 (High). CVSS vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H. EPSS exploitation probability: 0.0%.

Which versions of Cisco are affected by CVE-2026-20051?

Cisco Nexus switches in our infrastructure are vulnerable to a Layer 2 traffic loop attack that could be triggered by an adjacent network attacker without authentication.

How to fix or mitigate CVE-2026-20051?

Within 24 hours: Inventory all Nexus 3600 and 9500-R switches in production and identify network segments using EVPN Layer 2 configurations. Within 7 days: Implement network segmentation to restrict Layer 2 adjacency to trusted sources only; disable EVPN L2 features if business operations permit. Within 30 days: Monitor vendor advisories for patch availability; conduct network redesign to reduce EVPN L2 exposure; escalate to Cisco TAC for workaround guidance specific to your deployment.

Cisco CVE-2026-20051

HIGH

Use of Uninitialized Variable (CWE-457)

2026-02-25 psirt@cisco.com

Cisco Denial Of Service

7.4

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

7.4 HIGH

AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Attack Vector

Adjacent

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:55 vuln.today

CVE Published

Feb 25, 2026 - 17:25 nvd

HIGH 7.4

DescriptionCVE.org

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. 

AnalysisAI

Cisco Nexus 3600 and 9500-R switches are vulnerable to Layer 2 traffic loops when processing maliciously crafted EVPN frames, allowing unauthenticated adjacent attackers to trigger a denial of service condition by overwhelming network bandwidth. An attacker can exploit this logic error in Layer 2 ingress packet processing by sending crafted Ethernet frames, causing VxLAN traffic loops that drop all data plane traffic. No patch is currently available for this vulnerability.

Technical ContextAI

exists in the a denial of component. 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.