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CVE-2025-40779: DHCPv4 Client Request Vulnerability in Kea

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Overview

This report addresses a significant vulnerability, CVE-2025-40779, found in the Kea DHCP server. If a DHCPv4 client sends a request containing specific options and Kea fails to find an appropriate subnet for the client, the `kea-dhcp4` process could abort, causing a system failure. This vulnerability affects multiple versions of Kea, and if exploited, could potentially lead to a system compromise or data leakage.

Vulnerability Summary

CVE ID: CVE-2025-40779
Severity: High (7.5 CVSS Score)
Attack Vector: DHCPv4 Client Request
Privileges Required: None
User Interaction: None
Impact: System compromise, data leakage

Affected Products

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Product | Affected Versions

Kea | 2.7.1 – 2.7.9
Kea | 3.0.0
Kea | 3.1.0

How the Exploit Works

The exploit works when a DHCPv4 client sends a request with specific options to the Kea server. If Kea fails to find an appropriate subnet for the client, the `kea-dhcp4` process aborts due to an assertion failure. This vulnerability only affects if the client request is unicast directly to Kea; broadcast messages are not impacted by this issue.

Conceptual Example Code

The vulnerability can be potentially exploited by sending a malformed DHCPv4 client request to the Kea server, as illustrated in the conceptual pseudo-code below:

DHCPv4_Request {
HOST: Kea_Server_IP
Specific_Options: Malicious_payload
Request_Type: Unicast
}

In this pseudo-code, a DHCPv4 request is sent to the Kea server with malicious payload placed within the specific options. This can trigger a failure in the `kea-dhcp4` process if Kea cannot find an appropriate subnet for the client.

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Disclaimer:

The information and code presented in this article are provided for educational and defensive cybersecurity purposes only. Any conceptual or pseudocode examples are simplified representations intended to raise awareness and promote secure development and system configuration practices.

Do not use this information to attempt unauthorized access or exploit vulnerabilities on systems that you do not own or have explicit permission to test.

Ameeba and its authors do not endorse or condone malicious behavior and are not responsible for misuse of the content. Always follow ethical hacking guidelines, responsible disclosure practices, and local laws.

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