# CVE-2026-80588: mptcp: reclaim forward-allocated memory on RX path errors

> An attacker can cause unbounded memory growth in the Linux kernel MPTCP receive path, leading to a 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:** 26 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-80588, GHSA-82qc-q32m-354f, UBUNTU-CVE-2026-80588

## What is CVE-2026-80588?

CVE-2026-80588 is a high-severity denial of service vulnerability in Linux, published on 26 Aug 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: reclaim forward-allocated memory on RX path errors

After commit 9db5b3cec4ec ("mptcp: borrow forward memory from subflow"),
errors in the receive path prior to queueing skbs into the receive
queue do not trigger forward-allocated memory reclaiming.

Prevent forward memory from growing unboundedly in pathological drop
scenarios by explicitly reclaiming memory when skbs are dropped.

## Which versions are affected by CVE-2026-80588?


## How do I fix CVE-2026-80588?

Apply the vendor's patch.

## Is CVE-2026-80588 being exploited?

There is no known exploitation of CVE-2026-80588 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80588 and fix it if it is affected.

What it is: CVE-2026-80588 is a high-severity denial of service vulnerability in Linux, published on 26 Aug 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-2026-80588 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-2026-80588/ (Markdown: https://insights.sbomify.com/CVE-2026-80588/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80588
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80588
- OSV: https://osv.dev/vulnerability/CVE-2026-80588

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80588/
Summaries are generated and may contain mistakes; the official description above is the record.