CVE-2026-20171
MEDIUMDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 38% of all known CVEs.
References
Related Vulnerabilities
Other CWE-670 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2020-9425 | High | 7.5 | 17% | - | Fix |
| CVE-2019-9946 | High | 7.5 | 3.1% | - | Fix |
| CVE-2024-32896 | High | 7.8 | 3.0% | KEV | - |
| CVE-2019-17192 | Critical | 9.8 | 2.7% | - | - |
| CVE-2026-38361 | High | 7.5 | 2.6% | - | - |
| CVE-2020-1914 | Critical | 9.8 | 2.5% | - | Fix |
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-20.