VULNERABILITY INTELLIGENCE
CVE-2026-20171
CVSS score6.8 MEDIUM
EPSS probability0.47%
CISA KEVNot currently listed
Published2026-05-20
Last modified2026-07-23
CVSS vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
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.
Weakness classification
- CWE-670: Always-Incorrect Control Flow Implementation