CVE-2026-20171
MediumCVSS 6.8Exploitation Probability (EPSS)
Low risk38th percentile - higher than 38% of all known CVEs
Summary
Cisco Nexus 3000 and 9000 Series Switches in standalone NX-OS mode have a vulnerability in the BGP enforce-first-as feature. Incorrect parsing of a transitive BGP attribute allows an unauthenticated, remote attacker to trigger BGP session flaps, leading to denial of service.
Risk Assessment
A remote attacker can cause BGP routing instability, leading to network communication disruptions.
Recommendation
Apply the NX-OS software update from Cisco that contains the fix.
Original NVD description (English source)
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.