# CVE-2026-97524: mptcp: avoid unneeded actions on subflow reset

> A recursion loop in the Linux kernel MPTCP receive path can cause excessive processing and resource consumption, leading to denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104583, BELL-CVE-2026-97524, DEBIAN-CVE-2026-97524, GHSA-wphv-p3gw-h29j, UBUNTU-CVE-2026-97524

## What is CVE-2026-97524?

CVE-2026-97524 is a high-severity denial of service vulnerability in Linux, published on 25 Sep 2026. 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: avoid unneeded actions on subflow reset

Once in a blue moon, the mptcp receive path can recursively call
mptcp_data_ready() via state change under unlucky error conditions, and
then try to hold the data lock again.

Break the recursion loop explicitly checking for the exceptional
condition.

Add a new flag instead of using an existing one like 'closing', to exit
early in subflow_state_change(), and explicitly flush the RX queue at
reset time.

This avoids unneeded processing to check for available data -- calling
get_mapping_status() and more on a dying subflow -- but also in error
reporting and worker scheduling.

Note that we must consume the currently peeked skb before invoking
mptcp_dss_corruption to avoid consuming it again after the eventual
reset has freed it.

## Which versions are affected by CVE-2026-97524?


## How do I fix CVE-2026-97524?

Apply the vendor's patch.

## Is CVE-2026-97524 being exploited?

There is no known exploitation of CVE-2026-97524 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97524 and fix it if it is affected.

What it is: CVE-2026-97524 is a high-severity denial of service vulnerability in Linux, published on 25 Sep 2026. 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-2026-97524 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-2026-97524/ (Markdown: https://insights.sbomify.com/CVE-2026-97524/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97524
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97524
- OSV: https://osv.dev/vulnerability/CVE-2026-97524

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97524/
Summaries are generated and may contain mistakes; the official description above is the record.