Skip to content
Fencer Intel
critical 9.8

CVE-2026-121289 json

Security Advisory 0208

published yesterday modified yesterday also EUVD-2026-122810

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 51%
public exploits
0
none known

Summary

On affected platforms running Arista EOS with BGP configured, a specially crafted packet can cause the BGP agent to crash.

Successful exploitation causes the BGP agent process to terminate, resulting in the loss of all BGP sessions on the affected device and possible disruption to network routing until the process recovers. Due to the nature of the vulnerability, it may also be possible for a sophisticated attacker to achieve arbitrary code execution, which could compromise the confidentiality and integrity of the affected system.

Patch / fix

  • Arista Networks EOS 4.33.0F

Is CVE-2026-121289 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Exploit prediction

0.64% chance of exploitation in the next 30 days, higher than 51% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 4.0 9.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA 4.0 9.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • Arista Networks EOS

Classification

Weakness
  • CWE-121 Stack-based Buffer Overflow

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.