---
id: CVE-2026-64422
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes

  Reject invalid `net.ipv4.tcp_reordering` values before they reach TCP
  socket state
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes

  Reject invalid `net.ipv4.tcp_reordering` values before they reach TCP
  socket state. The sysctl is sto…
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H'
cwe:
  - CWE-190
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 2.6.24.1, < 5.10.261'
  - 'linux_kernel >= 5.11, < 5.15.212'
  - 'linux_kernel >= 5.16, < 6.1.178'
  - 'linux_kernel >= 6.2, < 6.6.145'
  - 'linux_kernel >= 6.7, < 6.12.96'
  - 'linux_kernel >= 6.13, < 6.18.39'
  - 'linux_kernel >= 6.19, < 7.1.4'
  - linux_kernel = 2.6.24
patched:
  - linux_kernel 7.1.4
published: '2026-07-25'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T09:18:19.287'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-64422'
references:
  - url: 'https://git.kernel.org/stable/c/27ddf4486c7dbf5bdd393fa8bef6b67179796d98'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/99206ce2244f8a3ed64298d0667c9055845a5dc7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a094ac95d3b69adfa1676eb9c8eae6835d4f1671'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/bbae351c0f32f7c200249e4aa6561b2b419dcf69'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e81f805824a8109504fce090641b17d135b48cd1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/efb8763d7bbb40cff4cc55a6b62c3095a038149c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f0d88a4cd03affff6c08adf6c63964e235aede43'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-019113.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00178
epssPercentile: 0.06502
ingestedAt: '2026-09-08T15:33:26.949Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes

Reject invalid `net.ipv4.tcp_reordering` values before they reach TCP
socket state. The sysctl is stored as an `int` but copied into the
`u32` `tp->reordering` field for new sockets, so negative writes wrap
to large values.

With `tcp_mtu_probing=2`, the wrapped value can overflow the
`tcp_mtu_probe()` size calculation and drive the MTU probing path into
an out-of-bounds read. Route `tcp_reordering` writes through
`proc_dointvec_minmax()` and require it to be at least 1. Also require
`tcp_max_reordering` to be at least 1 so the configured maximum cannot
become negative either.

When registering the table for a non-init network namespace, relocate
`extra2` pointers that refer into `init_net.ipv4` so the
`tcp_reordering` upper bound follows that namespace's
`tcp_max_reordering`.

Harden `tcp_mtu_probe()` itself by computing `size_needed` as `u64`.
This keeps the send queue and window checks from being bypassed through
signed integer overflow.

## Affected

- `linux_kernel >= 2.6.24.1, < 5.10.261`
- `linux_kernel >= 5.11, < 5.15.212`
- `linux_kernel >= 5.16, < 6.1.178`
- `linux_kernel >= 6.2, < 6.6.145`
- `linux_kernel >= 6.7, < 6.12.96`
- `linux_kernel >= 6.13, < 6.18.39`
- `linux_kernel >= 6.19, < 7.1.4`
- `linux_kernel = 2.6.24`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.1.4`