# CVE-2025-39976: futex: Use correct exit on failure from futex_hash_allocate_default()

> Incorrect error handling in Linux kernel futex allocation can cause a crash by unlocking unheld locks, leading to denial of service.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 15 Oct 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-39976, DEBIAN-CVE-2025-39976, GHSA-rgc5-qvp4-69x6, UBUNTU-CVE-2025-39976

## What is CVE-2025-39976?

CVE-2025-39976 is a high-severity vulnerability in Linux, published on 15 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

futex: Use correct exit on failure from futex_hash_allocate_default()

copy_process() uses the wrong error exit path from futex_hash_allocate_default().
After exiting from futex_hash_allocate_default(), neither tasklist_lock
nor siglock has been acquired. The exit label bad_fork_core_free unlocks
both of these locks which is wrong.

The next exit label, bad_fork_cancel_cgroup, is the correct exit.
sched_cgroup_fork() did not allocate any resources that need to freed.

Use bad_fork_cancel_cgroup on error exit from futex_hash_allocate_default().

## Which versions are affected by CVE-2025-39976?


## How do I fix CVE-2025-39976?

Apply the vendor's patch.

## Is CVE-2025-39976 being exploited?

There is no known exploitation of CVE-2025-39976 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-39976 and fix it if it is affected.

What it is: CVE-2025-39976 is a high-severity vulnerability in Linux, published on 15 Oct 2025. 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-2025-39976 in the wild and no public exploit code.

Affected product: Linux. 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-2025-39976/ (Markdown: https://insights.sbomify.com/CVE-2025-39976/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39976
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39976
- OSV: https://osv.dev/vulnerability/CVE-2025-39976

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39976/
Summaries are generated and may contain mistakes; the official description above is the record.