# CVE-2021-29626: Use after free in FreeBSD

> An unprivileged process can read private data from other processes or the kernel due to a use-after-free flaw in copy-on-write logic.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Apr 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-h9f8-7jjc-4hg6

## What is CVE-2021-29626?

CVE-2021-29626 is a medium-severity use after free vulnerability in Freebsd Freebsd, published on 7 Apr 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In FreeBSD 13.0-STABLE before n245117, 12.2-STABLE before r369551, 11.4-STABLE before r369559, 13.0-RC5 before p1, 12.2-RELEASE before p6, and 11.4-RELEASE before p9, copy-on-write logic failed to invalidate shared memory page mappings between multiple processes allowing an unprivileged process to maintain a mapping after it is freed, allowing the process to read private data belonging to other processes or the kernel.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-29626?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2021-29626?

No fix has been published for CVE-2021-29626 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-29626 being exploited?

There is no known exploitation of CVE-2021-29626 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-2021-29626 and fix it if it is affected.

What it is: CVE-2021-29626 is a medium-severity use after free vulnerability in Freebsd Freebsd, published on 7 Apr 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-29626 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-2021-29626/ (Markdown: https://insights.sbomify.com/CVE-2021-29626/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-29626
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-29626
- OSV: https://osv.dev/vulnerability/CVE-2021-29626

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-29626/
Summaries are generated and may contain mistakes; the official description above is the record.