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CVE-2026-20171

Cisco Nexus 3000 and 9000 Series Border Gateway Protocol Denial of Service Vulnerability

Published: May 20, 2026Updated: May 20, 2026 Sources: CVE List NVD
NVD MITRE
6.8CVSS
MEDIUM

A vulnerability in the Border Gateway Protocol (BGP) enforce-first-as feature of Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, remote attacker to trigger BGP peer flaps, resulting in a denial of service (DoS) condition. This vulnerability is due to incorrect parsing of a transitive BGP attribute. An attacker could exploit this vulnerability by sending a crafted BGP update through an established BGP peer session. If the update propagates to an affected device, it could cause the device to drop the BGP session and flap with the BGP peer that is forwarding this update, resulting in a DoS condition.

EPSS Score
N/A
CISA KEV
Not in KEV
Exploits
0 Known
Remediation
No Fix Available

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:CC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High

Weaknesses

CWE-670

Affected Products

Cisco NX-OS Software
Cisco

Exploitability

0 exploit sources identified

Exploit details including PoC links, Metasploit modules, and scanner templates are available after registration.

View exploit details

References

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-bgp-iefab-3hb2pwtx
sec.cloudapps.cisco.com

Timeline

Published
May 20, 2026
Last Updated
May 20, 2026

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