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VulnerabilityPublished

CVE-2026-121290: Arista Networks EOS · Unprotected Alternate Channel

Affects Arista Networks EOSSource CVE Database V5

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Not known to be exploited · CVSS 8.2 High : upgrade to 4.33.0F or 4.32.0F soon.

Data as of 10 Nov 2026, 20:32 UTC

CVSS 3.1 base score
8.2High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (Arista)CVSS 3.18.2
CNA (Arista)CVSS 4.08.3
Patch
Available – fixed in 4.33.0F, 4.32.0F
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

Upgrade Arista Networks EOS to 4.33.0F or 4.32.0F.

Affected software

ProductAffectedFixed in
Arista NetworksEOSAffected
  • >=4.36.0F <=4.36.2F
  • >=4.35.0F <=4.35.6M
  • >=4.34.0F <=4.34.8M
  • >=4.33.0F <=4.33.10M
  • >=4.32.0F <4.33.0F
  • >=1.0.0 <4.32.0F
Fixed in
  • 4.33.0F
  • 4.32.0F

AI-suggested

A fix is available in Arista EOS versions 4.32.0F and 4.33.0F and later. Users should upgrade to these or later versions to remediate the vulnerability. Since this is not a cloud service, manual patching is required. No additional mitigation steps are indicated by the vendor advisory.

Description

CVE-2026-121290 is a vulnerability in Arista Networks EOS affecting Border Gateway Protocol (BGP) configurations. Changing the BGP listen port from its default disables the default protective Access Control List (ACL) rules that guard against unexpected BGP peering attempts. This can lead to unauthorized BGP connections, potentially impacting system availability.

References

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