Riskcovery

CVE-2026-20171

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

State
Published
Severity
6.8 Medium
Published
May 20, 2026
Updated
May 20, 2026
Reserved
Oct 8, 2025

Read the record on cve.org

Description

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.

Scores

CVSSScoreVectorSource
3.16.8 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:Hcisco

Weaknesses

  • CWE-670 Always-Incorrect Control Flow Implementation

Affected Products

ProductVersions
Cisco NX-OS SoftwareCisco
  • 10.2(1)Affected
  • 10.2(1q)Affected
  • 10.2(2)Affected
  • 10.2(3)Affected
  • 10.2(3t)Affected
  • 10.2(2a)Affected
  • 10.3(1)Affected
  • 10.2(4)Affected
  • 10.3(2)Affected
  • 10.3(3)Affected
  • 10.2(5)Affected
  • 10.2(3v)Affected
  • 10.4(1)Affected
  • 10.3(99w)Affected
  • 10.2(6)Affected
  • 10.3(3w)Affected
  • 10.3(99x)Affected
  • 10.3(3o)Affected
  • 10.3(4)Affected
  • 10.3(3p)Affected
  • 10.3(4a)Affected
  • 10.4(2)Affected
  • 10.3(3q)Affected
  • 10.3(5)Affected
  • 10.2(7)Affected
  • and 24 more versions

References

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