---
id: CVE-2026-31495
title: 'netfilter: ctnetlink: use netlink policy range checks'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  netfilter: ctnetlink: use netlink policy range checks

  Replace manual range and mask validations with netlink policy
  annotations in ctnetlink code paths, so that the ne…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 <
    435b576cd2faa75154777868f8cbb73bf71644d3
  - >-
    Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 <
    2ef71307c86a9f866d6e28f1a0c06e2e9d794474
  - >-
    Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 <
    4f7d25f3f0786402ba48ff7d13b6241d77d975f5
  - >-
    Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 <
    fcec5ce2d73a41668b24e3f18c803541602a59f6
  - >-
    Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 <
    675c913b940488a84effdeeac5a1cfb657b59804
  - >-
    Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 <
    c6cb41eaae875501eaaa487b8db6539feb092292
  - >-
    Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 <
    45c33e79ae705b7af97e3117672b6cd258dd0b1b
  - >-
    Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 <
    8f15b5071b4548b0aafc03b366eb45c9c6566704
  - Linux 2.6.22
published: '2026-04-22'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T08:47:26.322Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31495'
references:
  - url: 'https://git.kernel.org/stable/c/435b576cd2faa75154777868f8cbb73bf71644d3'
  - url: 'https://git.kernel.org/stable/c/2ef71307c86a9f866d6e28f1a0c06e2e9d794474'
  - url: 'https://git.kernel.org/stable/c/4f7d25f3f0786402ba48ff7d13b6241d77d975f5'
  - url: 'https://git.kernel.org/stable/c/fcec5ce2d73a41668b24e3f18c803541602a59f6'
  - url: 'https://git.kernel.org/stable/c/675c913b940488a84effdeeac5a1cfb657b59804'
  - url: 'https://git.kernel.org/stable/c/c6cb41eaae875501eaaa487b8db6539feb092292'
  - url: 'https://git.kernel.org/stable/c/45c33e79ae705b7af97e3117672b6cd258dd0b1b'
  - url: 'https://git.kernel.org/stable/c/8f15b5071b4548b0aafc03b366eb45c9c6566704'
tags:
  - cve.org
epss: 0.00129
epssPercentile: 0.02875
ingestedAt: '2026-09-08T15:33:26.990Z'
---

## Overview

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

netfilter: ctnetlink: use netlink policy range checks

Replace manual range and mask validations with netlink policy
annotations in ctnetlink code paths, so that the netlink core rejects
invalid values early and can generate extack errors.

- CTA_PROTOINFO_TCP_STATE: reject values > TCP_CONNTRACK_SYN_SENT2 at
  policy level, removing the manual >= TCP_CONNTRACK_MAX check.
- CTA_PROTOINFO_TCP_WSCALE_ORIGINAL/REPLY: reject values > TCP_MAX_WSCALE
  (14). The normal TCP option parsing path already clamps to this value,
  but the ctnetlink path accepted 0-255, causing undefined behavior when
  used as a u32 shift count.
- CTA_FILTER_ORIG_FLAGS/REPLY_FLAGS: use NLA_POLICY_MASK with
  CTA_FILTER_F_ALL, removing the manual mask checks.
- CTA_EXPECT_FLAGS: use NLA_POLICY_MASK with NF_CT_EXPECT_MASK, adding
  a new mask define grouping all valid expect flags.

Extracted from a broader nf-next patch by Florian Westphal, scoped to
ctnetlink for the fixes tree.

## Affected

- `Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 < 435b576cd2faa75154777868f8cbb73bf71644d3`
- `Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 < 2ef71307c86a9f866d6e28f1a0c06e2e9d794474`
- `Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 < 4f7d25f3f0786402ba48ff7d13b6241d77d975f5`
- `Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 < fcec5ce2d73a41668b24e3f18c803541602a59f6`
- `Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 < 675c913b940488a84effdeeac5a1cfb657b59804`
- `Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 < c6cb41eaae875501eaaa487b8db6539feb092292`
- `Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 < 45c33e79ae705b7af97e3117672b6cd258dd0b1b`
- `Linux >= c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4 < 8f15b5071b4548b0aafc03b366eb45c9c6566704`
- `Linux 2.6.22`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.