# CVE-2026-53183: mptcp: allow subflow rcv wnd to shrink

> A flaw in the Linux kernel MPTCP implementation allows remote attackers to cause a denial of service by exhausting receiver buffer memory.

- **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 Jun 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-90404, BELL-CVE-2026-53183, DEBIAN-CVE-2026-53183, GHSA-wxvq-pwv2-xpc3, ROOT-OS-DEBIAN-12-CVE-2026-53183, ROOT-OS-UBUNTU-2404-CVE-2026-53183, UBUNTU-CVE-2026-53183

## What is CVE-2026-53183?

CVE-2026-53183 is a high-severity denial of service vulnerability in Linux kernel, published on 25 Jun 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: allow subflow rcv wnd to shrink

In MPTCP connection, the `window` field in the TCP header refers to the
MPTCP-level rcv_nxt and it's right edge should not move backward. Such
constraint is enforced at DSS option generation time.

At the same time, the TCP stack ensures independently that the TCP-level
rcv wnd right's edge does not move backward. That in turn causes artificial
inflating of the MPTCP rcv window when the incoming data is acked at the
TCP level and is OoO in the MPTCP sequence space (or lands in the backlog).

As a consequence, the incoming traffic can exceed the receiver rcvbuf size
even when the sender is not misbehaving.

Prevent such scenario forcibly allowing the TCP subflow to shrink the
TCP-level rcv wnd regardless of the current netns setting.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-53183?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53183?

Apply the vendor's patch.

## Is CVE-2026-53183 being exploited?

There is no known exploitation of CVE-2026-53183 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-2026-53183 and fix it if it is affected.

What it is: CVE-2026-53183 is a high-severity denial of service vulnerability in Linux kernel, published on 25 Jun 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-2026-53183 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-2026-53183/ (Markdown: https://insights.sbomify.com/CVE-2026-53183/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53183
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53183
- OSV: https://osv.dev/vulnerability/CVE-2026-53183

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53183/
Summaries are generated and may contain mistakes; the official description above is the record.