Arista EOS up to 4.33.9M/4.34.7.1M/4.35.5M/4.36.1F DHCP denial of service

Summaryinfo

A vulnerability marked as very critical has been reported in Arista EOS up to 4.33.9M/4.34.7.1M/4.35.5M/4.36.1F. Impacted is an unknown function of the component DHCP Handler. The manipulation leads to denial of service. This vulnerability is traded as CVE-2026-73437. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in Arista EOS up to 4.33.9M/4.34.7.1M/4.35.5M/4.36.1F. This issue affects an unknown code of the component DHCP Handler. The manipulation with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

On affected platforms running Arista EOS with Dynamic Host Configuration Protocol (DHCP) relay configured, an unauthenticated attacker with network access could send a crafted DHCP reply packet from an IP address that is not configured as a helper address, and the relay agent would forward it to clients without validating the source. This could allow the attacker to supply clients with malicious network configuration parameters, potentially resulting in traffic interception or denial of service for affected clients.

The advisory is shared at arista.com. The identification of this vulnerability is CVE-2026-73437 since 08/12/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/15/2026). MITRE ATT&CK project uses the attack technique T1499 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• Arista

Name

• EOS

Version

• 4.33.9M
• 4.34.7.1M
• 4.35.5M
• 4.36.1F

License

• commercial

CPE 2.3info

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CPE 2.2info

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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