What is CVE-2026-121290?

CVE-2026-121290 is a high-severity vulnerability in Arista Networks Eos, classified under Unprotected Alternate Channel. CVSS score: 8.2/10. Published 2026-11-10.

How severe is CVE-2026-121290?

High severity. CVSS v3 base score is 8.2 out of 10.

Vulnerability in Arista Networks Eos

CVE-2026-121290

On affected platforms running Arista EOS with Border Gateway Protocol (BGP) changing the BGP listen port from its default value disables default protective Access Control List (ACL) rules against unexpected BGP peering attempts.

Published 2026-11-10.

CVSS v3 metric

CVSS v3 base score 8.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Arista Networks Eos

Weakness classification (CWE)

CWE-420 — Unprotected Alternate Channel

References

www.arista.com/en/support/advisories-notices/security-advisory/25031-security-a… (vendor-advisory)

Frequently asked questions

What is CVE-2026-121290?: CVE-2026-121290 is a high-severity vulnerability in Arista Networks Eos, classified under Unprotected Alternate Channel. CVSS score: 8.2/10. Published 2026-11-10.
How severe is CVE-2026-121290?: High severity. CVSS v3 base score is 8.2 out of 10.