# CVE-2025-38552: mptcp: plug races between subflow fail and subflow creation

> A race condition in the Linux kernel MPTCP subsystem between subflow failure and creation can lead to system instability or denial of service.

- **Severity:** Critical 9.4 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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:** Yes
- **Published:** 16 Aug 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-66329, BELL-CVE-2025-38552, DEBIAN-CVE-2025-38552, GHSA-h9hh-vjgw-q6wq, ROOT-OS-DEBIAN-12-CVE-2025-38552, ROOT-OS-DEBIAN-13-CVE-2025-38552, ROOT-OS-UBUNTU-2204-CVE-2025-38552, ROOT-OS-UBUNTU-2404-CVE-2025-38552, UBUNTU-CVE-2025-38552

## What is CVE-2025-38552?

CVE-2025-38552 is a critical vulnerability in Debian Debian Linux, published on 16 Aug 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

mptcp: plug races between subflow fail and subflow creation

We have races similar to the one addressed by the previous patch between
subflow failing and additional subflow creation. They are just harder to
trigger.

The solution is similar. Use a separate flag to track the condition
'socket state prevent any additional subflow creation' protected by the
fallback lock.

The socket fallback makes such flag true, and also receiving or sending
an MP_FAIL option.

The field 'allow_infinite_fallback' is now always touched under the
relevant lock, we can drop the ONCE annotation on write.

## Which versions are affected by CVE-2025-38552?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-38552?

Apply the vendor's patch.

## Is CVE-2025-38552 being exploited?

There is no known exploitation of CVE-2025-38552 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-38552 and fix it if it is affected.

What it is: CVE-2025-38552 is a critical vulnerability in Debian Debian Linux, published on 16 Aug 2025. 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-2025-38552 in the wild and no public exploit code.

Affected product: Debian Debian 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-2025-38552/ (Markdown: https://insights.sbomify.com/CVE-2025-38552/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38552
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38552
- OSV: https://osv.dev/vulnerability/CVE-2025-38552

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38552/
Summaries are generated and may contain mistakes; the official description above is the record.