TI-2026-16265 Aliases CVE-2026-20051 GHSA-4466-83q5-3rxw

Cisco Nexus 3600-R and 9500-R Series Switching Platforms Layer 2 Loop Denial of Service Vulnerability

LOW 32CWE-457Published 2026-02-25 · Updated 2026-02-25

Key facts

Attack vector: Adjacent network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-457 and the CVSS impact.

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 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. 

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00173 6th percentileScored 2026-11-07

Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Cisco	Cisco NX-OS Software	9.2(3); 9.2(2v); 9.2(1); 9.2(2t); 9.2(3y); 9.3(2); 9.2(4); 9.3(1); 9.3(1z); 9.2(2); 9.3(3); 9.3(4); 9.3(5); 9.3(6); 9.3(5w); 9.3(7); 9.3(7k); 10.2(1); 9.3(7a); 9.3(8); 10.2(1q); 10.2(2); 9.3(9); 10.2(3); 10.2(3t); 9.3(10); 10.2(2a); 10.3(1); 10.2(4); 10.3(2); 9.3(11); 10.3(3); 10.2(5); 9.3(12); 10.2(3v); 10.4(1); 10.2(6); 10.3(3w); 10.3(3o); 10.3(4); 10.3(3p); 10.3(4a); 10.4(2); 10.3(3q); 9.3(13); 10.3(5); 10.2(7); 10.4(3); 10.3(3x); 10.3(4g); 10.5(1); 10.2(8); 10.3(3r); 10.3(6); 9.3(14); 10.4(4); 10.3(4h); 10.5(2); 10.3(7); 10.4(5); 10.5(3); 10.2(9); 9.3(15); 10.4(4g); 10.5(4); 10.6(1); 10.5(3t); 10.3(8); 10.4(6); 10.5(3s); 10.5(3e); 10.5(3o); 9.3(16); 10.6(1s); 10.5(3p)	—	No fix listed	CNA

Cisco NX-OS Software VendorCisco Affected 9.2(3); 9.2(2v); 9.2(1); 9.2(2t); 9.2(3y); 9.3(2); 9.2(4); 9.3(1); 9.3(1z); 9.2(2); 9.3(3); 9.3(4); 9.3(5); 9.3(6); 9.3(5w); 9.3(7); 9.3(7k); 10.2(1); 9.3(7a); 9.3(8); 10.2(1q); 10.2(2); 9.3(9); 10.2(3); 10.2(3t); 9.3(10); 10.2(2a); 10.3(1); 10.2(4); 10.3(2); 9.3(11); 10.3(3); 10.2(5); 9.3(12); 10.2(3v); 10.4(1); 10.2(6); 10.3(3w); 10.3(3o); 10.3(4); 10.3(3p); 10.3(4a); 10.4(2); 10.3(3q); 9.3(13); 10.3(5); 10.2(7); 10.4(3); 10.3(3x); 10.3(4g); 10.5(1); 10.2(8); 10.3(3r); 10.3(6); 9.3(14); 10.4(4); 10.3(4h); 10.5(2); 10.3(7); 10.4(5); 10.5(3); 10.2(9); 9.3(15); 10.4(4g); 10.5(4); 10.6(1); 10.5(3t); 10.3(8); 10.4(6); 10.5(3s); 10.5(3e); 10.5(3o); 9.3(16); 10.6(1s); 10.5(3p) Fixed in — No fix listed CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:o:cisco:nx-os::::::::	—	—	Cisco

cpe:2.3:o:cisco:nx-os:*:*:*:*:*:*:*:* Versions — — ·Cisco

Remediation

No fixed version listed by the sources yet.

Timeline

2026-10-02 Threatist record created from CVE-2026-20051
2026-10-03 Alias added: GHSA-4466-83q5-3rxw

References

Other 1

cisco-sa-nxos-ether-dos-Kv8YNWZ4

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TI-2026-53488 Cisco Identity Services Engine Authentication Bypass Vulnerability KEVCVSS 3.1CRITICAL 10.0
TI-2026-16388 Cisco Catalyst SD-WAN Controller Authentication Bypass Vulnerability KEVCVSS 3.1CRITICAL 10.0
TI-2026-16344 Cisco Secure Firewall Management Center Software Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 10.0

See all 7059 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences