CVE-2025-40779
Description
A vulnerability was found in Kea. When an attacker who is an existing client with an assigned IP sends a crafted unicast packet directly to the server's IP and Kea cannot find any subnets that match that client's credentials, the server crashes causing a Denial of Service via assertion/NULL-path failure. This vulnerability does not persist for broadcast packets because they ignore such unverifiable clients.
Statement
This flaw is marked IMPORTANT because a single unicast packet that does not have a subnet match can crash the server, preventing all DHCP clients it serves from obtaining new leases or renewing existing ones until the service is restarted. In this case, Red Hat customers who run Kea service on platforms like RHEL wont be able to access Kea if this vulnerability is triggered. Kea is a DHCP Server that is responsible for assigning IPv4/IPv6 addresses and network parameters to clients. The kea-dhcp4 process handles IPv4 requests, selecting subnets and leases based on client options. This flaw causes kea-dhcp4 to abort after assertion and crash the Kea server if the unicast DHCPv4 request includes certain options that fail subnet selection.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
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