What’s Vulnerable › Vulnerabilities
CVE-2026-20171: Cisco Nexus 3000 and 9000 Series Border Gateway Protocol Denial of Service Vulnerability
- Severity: medium (CVSS 6.8 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.5% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-05-20 · updated 2026-07-23
- Weakness: CWE-670
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.
Affected products
- Cisco NX-OS: 10.2(1), 10.2(1q), 10.2(2), 10.2(3), 10.2(3t), 10.2(2a) (+43)
References
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