# CVE-2009-4141: Use after free in n/a

> Local attackers can gain privileges via a use-after-free in the Linux kernel's fasync_helper function when manipulating file locks and async flags.

- **Severity:** High 7.2 (`AV:L/AC:L/Au:N/C:C/I:C/A:C`)
- **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:** Yes
- **Published:** 19 Jan 2010
- **Updated:** 7 Aug 2024
- **Also known as:** GHSA-45gx-j644-hhf5

## What is CVE-2009-4141?

CVE-2009-4141 is a high-severity use after free vulnerability in Linux kernel, published on 19 Jan 2010. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Use-after-free vulnerability in the fasync_helper function in fs/fcntl.c in the Linux kernel before 2.6.33-rc4-git1 allows local users to gain privileges via vectors that include enabling O_ASYNC (aka FASYNC or FIOASYNC) on a locked file, and then closing this file.

Weakness: CWE-399

## Which versions are affected by CVE-2009-4141?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2009-4141?

Apply the vendor's patch.

## Is CVE-2009-4141 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2009-4141 exists.

Public exploit code:

- Linux Kernel < 2.6.28 - 'fasync_helper()' Local Privilege Escalation (exploitdb)

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2009-4141 and fix it if it is affected.

What it is: CVE-2009-4141 is a high-severity use after free vulnerability in Linux kernel, published on 19 Jan 2010. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2009-4141 exists.

Affected product: Linux kernel. 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-2009-4141/ (Markdown: https://insights.sbomify.com/CVE-2009-4141/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2009-4141
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2009-4141
- OSV: https://osv.dev/vulnerability/CVE-2009-4141

---
From sbomify Insights: https://insights.sbomify.com/CVE-2009-4141/
Summaries are generated and may contain mistakes; the official description above is the record.