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CVE-2026-121289

CRITICALCVSS 9.8/10EPSS 0.64%

Last modified

CVE-2026-121289 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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.. EPSS estimates a 0.64% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1
9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS 4.0
9.3/10

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

EPSS Probability
0.64%

51.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
Arista NetworksEOS>= 4.36.0F, <= 4.36.2F; >= 4.35.0F, <= 4.35.6M; >= 4.34.0F, <= 4.34.8M; >= 4.33.0F, <= 4.33.10M; >= 4.25.1F, < 4.33.0F

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-121289?
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.
How severe is CVE-2026-121289?
CVE-2026-121289 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.64% probability of exploitation in the next 30 days.
How do I fix CVE-2026-121289?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST