🔐 CVE Alert

CVE-2026-20171

MEDIUM 6.8

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

CVSS Score
6.8
EPSS Score
0.0%
EPSS Percentile
0th

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.

CWE CWE-670
Vendor cisco
Product cisco nx-os software
Ecosystems
Industries
NetworkingTelecommunications
Published May 20, 2026
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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

Affected Versions

Cisco / Cisco NX-OS Software
10.2(1) 10.2(1q) 10.2(2) 10.2(3) 10.2(3t) 10.2(2a) 10.3(1) 10.2(4) 10.3(2) 10.3(3) 10.2(5) 10.2(3v) 10.4(1) 10.3(99w) 10.2(6) 10.3(3w) 10.3(99x) 10.3(3o) 10.3(4) 10.3(3p) 10.3(4a) 10.4(2) 10.3(3q) 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) 10.4(4) 10.3(4h) 10.5(2) 10.3(7) 10.4(5) 10.5(3) 10.2(9) 10.4(4g) 10.6(1) 10.5(3t) 10.3(8) 10.4(6) 10.5(3s) 10.5(3e) 10.5(3o) 10.6(1s) 10.5(3p)

References

NVD ↗ CVE.org ↗ EPSS Data ↗
sec.cloudapps.cisco.com: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-bgp-iefab-3hb2pwtx