Arista EOS up to 4.36.2F BGP input validation

Summaryinfo

A vulnerability, which was classified as very critical, has been found in Arista EOS up to 4.32.x/4.33.10M/4.34.8M/4.35.6M/4.36.2F. This issue affects some unknown processing of the component BGP. The manipulation leads to input validation. This vulnerability is listed as CVE-2026-121289. The attack may be initiated remotely. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in Arista EOS up to 4.32.x/4.33.10M/4.34.8M/4.35.6M/4.36.2F. This issue affects an unknown functionality of the component BGP. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at arista.com. The identification of this vulnerability is CVE-2026-121289 since 11/03/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 11/10/2026).

Upgrading to version 4.33.0F eliminates this vulnerability.

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Productinfo

Vendor

• Arista

Name

• EOS

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4
• 4.5
• 4.6
• 4.7
• 4.8
• 4.9
• 4.10
• 4.11
• 4.12
• 4.13
• 4.14
• 4.15
• 4.16
• 4.17
• 4.18
• 4.19
• 4.20
• 4.21
• 4.22
• 4.23
• 4.24
• 4.25
• 4.26
• 4.27
• 4.28
• 4.29
• 4.30
• 4.31
• 4.32
• 4.33.10M
• 4.34.8M
• 4.35.6M
• 4.36.2F

License

• commercial

CPE 2.3info

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CPE 2.2info

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