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VulnerabilityPublished

CVE-2026-121368: Arista Networks EOS · Out-of-bounds Write

Affects Arista Networks EOSSource CVE Database V5

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Not known to be exploited · CVSS 8.6 High : upgrade to 4.33.0F or 4.32.0F soon.

Data as of 10 Nov 2026, 20:22 UTC

CVSS 3.1 base score
8.6High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (Arista)CVSS 3.18.6
CNA (Arista)CVSS 4.08.9
Patch
Available – fixed in 4.33.0F, 4.32.0F
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/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

Fixed versions are available starting from 4.32.0F and 4.33.0F. Users should upgrade affected EOS versions to these or later releases to remediate the vulnerability. No vendor advisory content contradicts this; thus, patching is the recommended mitigation.

Description

CVE-2026-121368 is a high-severity vulnerability in Arista Networks EOS affecting versions from 1.0.0 up to 4.36.2F. It involves an out-of-bounds write triggered by specially crafted BFD packets when Bidirectional Forwarding Detection is configured with keyed MD5 or SHA1 authentication. An unauthenticated attacker with network adjacency can cause a system reboot, impacting availability.

References

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