# CVE-2026-97568: mptcp: syncookies: remember the request backup flag

> An uninitialized memory read in the Linux kernel MPTCP subsystem may leak sensitive kernel memory to remote attackers.

- **Severity:** Not scored
- **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-104529, BELL-CVE-2026-97568, DEBIAN-CVE-2026-97568, GHSA-6cg2-hrxf-655w, UBUNTU-CVE-2026-97568

## What is CVE-2026-97568?

CVE-2026-97568 is a 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: syncookies: remember the request backup flag

Instead of using an uninitialised bit when copying the info in
subflow_ulp_clone().

To fix this, no need to extend the join_entry structure: backup is
coming from struct mptcp_subflow_request_sock, only one bit. Do the same
here by using one bit for both.

## Which versions are affected by CVE-2026-97568?


## How do I fix CVE-2026-97568?

Apply the vendor's patch.

## Is CVE-2026-97568 being exploited?

There is no known exploitation of CVE-2026-97568 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97568 and fix it if it is affected.

What it is: CVE-2026-97568 is a 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-2026-97568 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-2026-97568/ (Markdown: https://insights.sbomify.com/CVE-2026-97568/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97568
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97568
- OSV: https://osv.dev/vulnerability/CVE-2026-97568

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97568/
Summaries are generated and may contain mistakes; the official description above is the record.