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CVE-2026-20051— Cisco Nexus 3600-R and 9500-R Series Switching Platforms Layer 2 Loop Denial of Service Vulnerability

Quick assessment

Affected
Cisco Cisco NX-OS Software
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Cisco Nexus 3600 Platform Switches和Cisco Nexus 9500 Series Switches都是美国思科（Cisco）公司的产品。Cisco Nexus 3600 Platform Switches是一款3600系列平台交换机。Cisco Nexus 9500 Series Switches是系列交换机。 Cisco Nexus 3600 Platform Switches和Cisco Nexus 9500 Series Switches存在安全漏洞，该漏洞源于处

CVSS 7.4 · High EPSS 0.16% · P5

Possible ATT&CK Techniques 1 AI

T1498 · Network Denial of Service
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I. Basic Information for CVE-2026-20051

Vulnerability Information
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Vulnerability Title
Cisco Nexus 3600-R and 9500-R Series Switching Platforms Layer 2 Loop Denial of Service Vulnerability
Source: CVE Program / CVE List V5
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. 
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
使用未经初始化的变量
Source: CVE Program / CVE List V5
Vulnerability Title
Cisco Nexus 3600 Platform Switches和Cisco Nexus 9500 Series Switches 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Cisco Nexus 3600 Platform Switches和Cisco Nexus 9500 Series Switches都是美国思科（Cisco）公司的产品。Cisco Nexus 3600 Platform Switches是一款3600系列平台交换机。Cisco Nexus 9500 Series Switches是系列交换机。 Cisco Nexus 3600 Platform Switches和Cisco Nexus 9500 Series Switches存在安全漏洞，该漏洞源于处
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Cisco Cisco NX-OS Software 9.2(3) -

II. Public POCs for CVE-2026-20051

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III. Intelligence Information for CVE-2026-20051

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Vendor Advisories for CVE-2026-20051 (1)

Same Patch Batch · Cisco · 2026-02-25 · 15 CVEs total

CVE-2026-20127 10.0 CRITICAL Cisco Catalyst SD-WAN Controller Authentication Bypass Vulnerability
CVE-2026-20129 9.8 CRITICAL Cisco Catayst SD-WAN Authentication Bypass Vulnerability
CVE-2026-20126 8.8 HIGH Cisco Catalyst SD-WAN Manager Privilege Escalation Vulnerability
CVE-2026-20048 7.7 HIGH Cisco NX-OS Software SNMP Denial of Service Vulnerability
CVE-2026-20128 7.5 HIGH Cisco Catalyst SD-WAN Manager Information Disclosure Vulnerability
CVE-2026-20033 7.4 HIGH Cisco NX-OS Software Denial of Service Vulnerability
CVE-2026-20010 7.4 HIGH Cisco Nexus 3000 and 9000 Series Switches Link Layer Discovery Protocol Denial of Service
CVE-2026-20099 6.7 MEDIUM Cisco UCS Manager and FXOS Software Command Injection Vulnerability
CVE-2026-20036 6.5 MEDIUM Cisco UCS Manager Software Command Injection Vulnerability
CVE-2026-20133 6.5 MEDIUM Cisco Catalyst SD-WAN Manager（Cisco SD-WAN vManage） 信息泄露漏洞
CVE-2026-20107 5.5 MEDIUM Cisco Application Policy Infrastructure Controller Denial of Service Vulnerability
CVE-2026-20122 5.4 MEDIUM Cisco Catalyst SD-WAN Manager Arbitrary File Overwrite Vulnerability
CVE-2026-20091 4.8 MEDIUM Cisco UCS Manager and FXOS Software Stored Cross-Site Scripting Vulnerability
CVE-2026-20037 4.4 MEDIUM Cisco UCS Manager File Write Vulnerability

IV. Related Vulnerabilities

Same product: Cisco NX-OS Software
Same vendor: Cisco
Same weakness: CWE-457

V. Comments for CVE-2026-20051

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