CVE-2026-20171

Name: CVE-2026-20171
Creator: NVD / NIST
Published: 2026-05-20T17:16:19.813+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.8/10EPSS 0.47%

Last modified Jun 17, 2026

This CVE is reserved or awaiting analysis. Details will appear once published by NVD.

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.

Metrics

CVSS 3.1

6.8/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H

EPSS Probability

0.47%

37.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-670

References

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

Timeline

Published: May 20, 2026
Last Modified: Jun 17, 2026
Status: Awaiting Analysis

Are you affected by CVE-2026-20171?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST