# CVE-2026-42512: Remotely triggerable out-of-bounds heap write in dhclient

> A heap buffer overflow in FreeBSD's dhclient allows remote attackers to cause a crash or potentially execute arbitrary code via crafted packets.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 30 Apr 2026
- **Updated:** 1 May 2026
- **Also known as:** GHSA-6r9j-w82p-v45p

## What is CVE-2026-42512?

CVE-2026-42512 is a high-severity memory corruption vulnerability in Freebsd Freebsd, published on 30 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-42512?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2026-42512?

No fix has been published for CVE-2026-42512 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-42512 being exploited?

There is no known exploitation of CVE-2026-42512 in the wild and no public exploit code.

## Other vulnerabilities in Freebsd Freebsd

- [CVE-2018-17160](https://insights.sbomify.com/CVE-2018-17160/): Memory corruption in FreeBSD (critical 10.0)
- [CVE-2014-3954](https://insights.sbomify.com/CVE-2014-3954/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-4304](https://insights.sbomify.com/CVE-2006-4304/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-0226](https://insights.sbomify.com/CVE-2006-0226/): Integer overflow in n/a (critical 10.0)
- [CVE-2004-0002](https://insights.sbomify.com/CVE-2004-0002/): Denial of service in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42512 and fix it if it is affected.

What it is: CVE-2026-42512 is a high-severity memory corruption vulnerability in Freebsd Freebsd, published on 30 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-42512 in the wild and no public exploit code.

Affected product: Freebsd Freebsd. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-42512/ (Markdown: https://insights.sbomify.com/CVE-2026-42512/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42512
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42512
- OSV: https://osv.dev/vulnerability/CVE-2026-42512

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42512/
Summaries are generated and may contain mistakes; the official description above is the record.