# CVE-2026-46170: mptcp: pm: ADD_ADDR rtx: free sk if last

> A use-after-free vulnerability in the Linux kernel MPTCP path manager allows attackers to cause a denial of service via improper socket reference counting during retransmissions.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 28 May 2026
- **Updated:** 14 Sep 2026
- **Also known as:** AZL-89091, BELL-CVE-2026-46170, DEBIAN-CVE-2026-46170, GHSA-xrpw-xx6g-3jg3, ROOT-OS-DEBIAN-11-CVE-2026-46170, ROOT-OS-DEBIAN-12-CVE-2026-46170, ROOT-OS-DEBIAN-13-CVE-2026-46170, ROOT-OS-UBUNTU-2204-CVE-2026-46170, ROOT-OS-UBUNTU-2404-CVE-2026-46170, UBUNTU-CVE-2026-46170

## What is CVE-2026-46170?

CVE-2026-46170 is a medium-severity use after free vulnerability in Linux kernel, published on 28 May 2026. 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:

mptcp: pm: ADD_ADDR rtx: free sk if last

When an ADD_ADDR is retransmitted, the sk is held in sk_reset_timer(),
and released at the end.

If at that moment, it was the last reference being held, the sk would
not be freed. sock_put() should then be called instead of __sock_put().

But that's not enough: if it is the last reference, sock_put() will call
sk_free(), which will end up calling sk_stop_timer_sync() on the same
timer, and waiting indefinitely to finish. So it is needed to mark that
the timer is done at the end of the timer handler when it has not been
rescheduled, not to call sk_stop_timer_sync() on "itself".

## Which versions are affected by CVE-2026-46170?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-46170?

Apply the vendor's patch.

## Is CVE-2026-46170 being exploited?

There is no known exploitation of CVE-2026-46170 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46170 and fix it if it is affected.

What it is: CVE-2026-46170 is a medium-severity use after free vulnerability in Linux kernel, published on 28 May 2026. 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-2026-46170 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-46170/ (Markdown: https://insights.sbomify.com/CVE-2026-46170/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46170
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46170
- OSV: https://osv.dev/vulnerability/CVE-2026-46170

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46170/
Summaries are generated and may contain mistakes; the official description above is the record.