CVE-2026-20171

MediumCVSS 6.8/10Last modified Jul 23, 2026

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 6.8/10CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H

Weakness enumeration

CWE-670

Affected software

Source: the vendor's advisory (CNA). NVD analysis pending.

No affected versions have been published.

Timeline

Published
May 20, 2026
Last modified
Jul 23, 2026
NVD status
Awaiting Analysis

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CVE-2026-20171: Medium severity, CVSS 6.8 | Vulnix