---
id: CVE-2026-53183
title: |-
  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 …
summary: |-
  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 …
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 5.19, < 6.1.176'
  - 'linux_kernel >= 6.2, < 6.6.143'
  - 'linux_kernel >= 6.7, < 6.12.94'
  - 'linux_kernel >= 6.13, < 6.18.36'
  - 'linux_kernel >= 6.19, < 7.0.13'
  - linux_kernel = 7.1
patched:
  - linux_kernel 7.0.13
published: '2026-06-25'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T02:20:03.540'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-53183'
references:
  - url: 'https://git.kernel.org/stable/c/653245266913f03fcf21cbca68eed5c197a33e52'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/aa3861f40ac32706d9e97bfac76984613e278788'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b1fd13074f22105deec45aa02283e322733e0c2d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/bf364b0f10b27679140699821f88af7f01e2a6e3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c297a4e65c50a2b807d9309b22615080faffa8f3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/da23be77e1292cd611e736c3aa17da633d7ddce7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-784472.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00479
epssPercentile: 0.39775
ingestedAt: '2026-10-15T03:30:12.907Z'
---

## Overview

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.

## Affected

- `linux_kernel >= 5.19, < 6.1.176`
- `linux_kernel >= 6.2, < 6.6.143`
- `linux_kernel >= 6.7, < 6.12.94`
- `linux_kernel >= 6.13, < 6.18.36`
- `linux_kernel >= 6.19, < 7.0.13`
- `linux_kernel = 7.1`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.0.13`