FreeBSD dhclient heap-based overflow

Summaryinfo

A vulnerability marked as critical has been reported in FreeBSD. This impacts an unknown function of the component dhclient. This manipulation causes heap-based overflow. The identification of this vulnerability is CVE-2026-42512. It is possible to initiate the attack remotely. There is no exploit available. To fix this issue, it is recommended to deploy a patch.

Detailsinfo

A vulnerability was found in FreeBSD (the affected version is unknown). It has been declared as critical. Affected by this vulnerability is an unknown code of the component dhclient. The manipulation with an unknown input leads to a heap-based overflow vulnerability. The CWE definition for the vulnerability is CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

As dhclient is building an environment to pass to dhclient-script, it may need to resize the array of string pointers. The code which expands the array incorrectly calculates its new size when requesting memory, resulting in a heap buffer overrun. A specially crafted packet can cause dhclient to overrun its buffer of environment entries. This can result in a crash, but it may be possible to leverage this bug to achieve remote code execution.

The weakness was shared with AISLE Research Team. It is possible to read the advisory at security.freebsd.org. This vulnerability is known as CVE-2026-42512 since 04/28/2026. The exploitation appears to be difficult. The attack can be launched remotely. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 05/01/2026).

Applying a patch is able to eliminate this problem.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-1324). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• FreeBSD Project FreeBSD OS

Productinfo

Type

• Operating System

Name

• FreeBSD

License

• open-source

Website

• Product: https://www.freebsd.org/

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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