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 |
Common questions
How do I fix CVE-2026-20171?
No published fix for CVE-2026-20171 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-20171 being actively exploited?
Not that we know of. CVE-2026-20171 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.47% is the estimated probability that it will be exploited in the next 30 days. That is higher than 38% of all scored CVEs.
How severe is CVE-2026-20171?
CVE-2026-20171 has a CVSS v3 base score of 6.8, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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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 2026-07-23.