CVE: 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
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.
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 or posted as confidential GitLab issues at https://gitlab.isc.org/isc-projects/kea/-/issues/new?issue[confidential]=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/.
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.
The Knowledgebase article https://kb.isc.org/docs/cve-2025-40779 is the complete and official security advisory document.
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