--- title: "CVE-2025-40779: Kea crash upon interaction between specific client options and subnet selection" slug: "cve-2025-40779" description: "If a DHCPv4 client sends a request with some specific options, and Kea fails to find an appropriate subnet for the client, the kea-dhcp4 process will abort with an assertion failure. This happens only if the client request is unicast directly to Kea; broadcast messages do not cause the problem." updated: 2025-08-27T14:17:08Z published: 2025-08-27T14:17:08Z --- > ## Documentation Index > Fetch the complete documentation index at: https://kb.isc.org/llms.txt > Use this file to discover all available pages before exploring further. # CVE-2025-40779: Kea crash upon interaction between specific client options and subnet selection **CVE:** [CVE-2025-40779](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-40779) **Title:** Kea crash upon interaction between specific client options and subnet selection **Document version:** 2.0 **Posting date:** 27 August 2025 **Program impacted:** [Kea](https://www.isc.org/kea/) **Versions affected:** Kea - 2.7.1 -> 2.7.9 - 3.0.0 - 3.1.0 **Versions NOT affected:** Kea - 2.6.0 -> 2.6.4 (Versions prior to 2.6.0 were not assessed.) Versions prior to 2.6.0 are likely unaffected, but were not assessed, as they are end-of-life (EOL). **Severity:** High **Exploitable:** Remotely **Description:** If a DHCPv4 client sends a request with some specific options, and Kea fails to find an appropriate subnet for the client, the `kea-dhcp4` process will abort with an assertion failure. This happens only if the client request is unicast directly to Kea; broadcast messages do not cause the problem. **Impact:** Denial of service. A malicious or misconfigured DHCP client can crash the Kea DHCPv4 service by sending a single packet. **CVSS Score:** 7.5 **CVSS Vector:** CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit: [https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H&version=3.1](https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H&version=3.1). **Workarounds:** No workarounds known. **Active exploits:** We are not aware of any active exploits. **Solution:** Upgrade to the patched release most closely related to your current version of Kea: - 3.0.1 - 3.1.1 **Acknowledgments:** ISC would like to thank the following for bringing this vulnerability to our attention: - Jochen M. - Martin Dinev, Trading212 - Ashwani Kumar, Post Graduate Institute of Medical Education & Research, Chandigarh, India - Bret Giddings, University of Essex - Florian Ritterhoff, Munich University of Applied Sciences **Document revision history:** - 1.0 Early Notification, 20 August 2025 - 2.0 Public disclosure, 27 August 2025 **Do you still have questions?** Questions regarding this advisory should be mailed to [kea-security@isc.org](mailto:kea-security@isc.org) or posted as confidential GitLab issues at [https://gitlab.isc.org/isc-projects/kea/-/issues/new?issue[confidential]=true](https://gitlab.isc.org/isc-projects/kea/-/issues/new?issue%5Bconfidential%5D=true). **Note:** ISC patches only currently supported versions. When possible we indicate EOL versions affected. For current information on which versions are actively supported, please see [https://www.isc.org/download/](https://www.isc.org/download/). **ISC Security Vulnerability Disclosure Policy:** Details of our current security advisory policy and practice can be found in the ISC Software Defect and Security Vulnerability Disclosure Policy at [https://kb.isc.org/docs/aa-00861](https://kb.isc.org/docs/aa-00861). The Knowledgebase article [https://kb.isc.org/docs/cve-2025-40779](https://kb.isc.org/docs/cve-2025-40779) is the complete and official security advisory document. **Legal Disclaimer:** Internet Systems Consortium (ISC) is providing this notice on an "AS IS" basis. No warranty or guarantee of any kind is expressed in this notice and none should be implied. ISC expressly excludes and disclaims any warranties regarding this notice or materials referred to in this notice, including, without limitation, any implied warranty of merchantability, fitness for a particular purpose, absence of hidden defects, or of non-infringement. Your use or reliance on this notice or materials referred to in this notice is at your own risk. ISC may change this notice at any time. A stand-alone copy or paraphrase of the text of this document that omits the document URL is an uncontrolled copy. Uncontrolled copies may lack important information, be out of date, or contain factual errors.