# CVE-2025-40331: sctp: Prevent TOCTOU out-of-bounds write

> A time-of-check to time-of-use race condition in the Linux kernel SCTP subsystem allows out-of-bounds writes, potentially leading to code execution or privilege escalation.

- **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:** 9 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40331, DEBIAN-CVE-2025-40331, GHSA-c4fm-qmm5-xqx8, ROOT-OS-DEBIAN-12-CVE-2025-40331, ROOT-OS-DEBIAN-13-CVE-2025-40331, ROOT-OS-UBUNTU-2204-CVE-2025-40331, ROOT-OS-UBUNTU-2404-CVE-2025-40331, UBUNTU-CVE-2025-40331

## What is CVE-2025-40331?

CVE-2025-40331 is a high-severity vulnerability in Linux, published on 9 Dec 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:

sctp: Prevent TOCTOU out-of-bounds write

For the following path not holding the sock lock,

  sctp_diag_dump() -> sctp_for_each_endpoint() -> sctp_ep_dump()

make sure not to exceed bounds in case the address list has grown
between buffer allocation (time-of-check) and write (time-of-use).

## Which versions are affected by CVE-2025-40331?


## How do I fix CVE-2025-40331?

Apply the vendor's patch.

## Is CVE-2025-40331 being exploited?

There is no known exploitation of CVE-2025-40331 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40331 and fix it if it is affected.

What it is: CVE-2025-40331 is a high-severity vulnerability in Linux, published on 9 Dec 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-2025-40331 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-2025-40331/ (Markdown: https://insights.sbomify.com/CVE-2025-40331/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40331
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40331
- OSV: https://osv.dev/vulnerability/CVE-2025-40331

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40331/
Summaries are generated and may contain mistakes; the official description above is the record.