November 13, 2026

CVE Watchtower

CVE-2026-121289Arista Networks EOS Stack-based Buffer Overflow

NVD

Vulnerability 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.
Severity Level
CRITICAL(9.3)
Published Date
Nov 10, 2026
Last Modified
Nov 13, 2026
Exploitation Status
No confirmed exploitation yet
EPSS Score (30-Day)
0.64%Probability
Root Weakness (CWE)
CWE-121: Stack-based Buffer Overflow ↗
The buffer being overwritten is allocated on the stack.
CVSS v4.0 Base Metrics — Score 9.3 (CRITICAL)
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
Attack VectorNetwork
Attack ComplexityLow
Attack RequirementsNone
Privileges RequiredNone
User InteractionNone
Confidentiality (Vulnerable System)High
Integrity (Vulnerable System)High
Availability (Vulnerable System)High
Confidentiality (Subsequent System)None
Integrity (Subsequent System)None
Availability (Subsequent System)None
Show CVSS v3.x metrics (score 9.8)
CVSS v3.1 Base Metrics — Score 9.8 (CRITICAL)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh

Affected & Patched Versions

Affected Versions
  • Arista Networks EOS >= 4.36.0F and <= 4.36.2F
  • Arista Networks EOS >= 4.35.0F and <= 4.35.6M
  • Arista Networks EOS >= 4.34.0F and <= 4.34.8M
  • Arista Networks EOS >= 4.33.0F and <= 4.33.10M
  • Arista Networks EOS >= 4.25.1F and < 4.33.0F
Patched Versions
  • Arista Networks EOS 4.36.2F
  • Arista Networks EOS 4.35.6M
  • Arista Networks EOS 4.34.8M
  • Arista Networks EOS 4.33.10M
  • Arista Networks EOS 4.33.0F

What to do

Plan remediation soon. No exploitation is confirmed yet, but the severity is critical.

  1. Check whether you run Arista Networks EOS and which version.
  2. Update to a patched version listed above, then confirm the new version.

Timeline

  • Nov 10, 2026Published
  • Nov 13, 2026Record last modified

Score, severity and exploitation changes are tracked from the day Watchtower started logging them.

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External References

Data last checked: Nov 13, 2026 18:23 UTC