CVE-2026-20051

highpriority · track · 0EPSS 0.002 · 7 %ileDEEUUS
grimoire priorityP2 · Scheduled
Exploitable?
—
no known exploitation
Likely / severe?
0.17% (7th) EPSS
CVSS 7.4 · high
Is it mine?
206 products
Check your exposure
Who says so?
4 sources
cnnvd · enisa_euvd · cert_bund · cisco_csaf

EPSS · scored 2026-10-27

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. 

01

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

02

cvss

Technical severity, 0–10. One row per scoring source.

7.4
010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.8–7.4

v3.17.4highCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:Hsecondary · ENISA EU
v3.17.4highCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:Hsecondary · psirt@cisco.com USexploitability 2.8 · impact 4
v3.16.8mediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:Usecondary · CVSS-BT (t0sche)
v3.17.4highCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:Hsecondary · Cisco PSIRT US
03

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-457US
04

affected products (206)

Products and version ranges known to be affected.

showing 20 of 206
05

advisories (2)

Vendor and ecosystem advisories describing this.

  • WID-SEC-W-2026-0523Cisco Nexus: Mehrere Schwachstellen ermöglichen Denial of ServiceDeutsch2026-02-25csaf · cert_bundDE

    Ein Angreifer kann mehrere Schwachstellen in Cisco Nexus ausnutzen, um einen Denial of Service Angriff durchzuführen.

  • cisco-sa-nxos-ether-dos-Kv8YNWZ4Cisco Nexus 3600 and 9500-R Series Switching Platforms Layer 2 Loop Denial of Service Vulnerability2026-02-25csaf · cisco_csafUS

    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. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is part of the February 2026 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: February 2026 Semiannual Cisco FXOS and NX-OS Software Security Advisory Bundled Publication ["https://sec.cloudapps.cisco.com/security/center/viewErp.x?alertId=ERP-75740"].

06

also known as (3)

Other names and identifiers for this entity.

07

sources

Which sources assert this record, and when.

cnnvdenisa_euvdcert_bundcisco_csafNVDCVE.orgMITRE
published 2026-02-25modified 2026-06-17
08

references (3)

External citations — patches, advisories, analysis.

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