---
id: CVE-2026-43383
title: 'net/tcp-md5: Fix MAC comparison to be constant-time'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/tcp-md5: Fix MAC comparison to be constant-time

  To prevent timing attacks, MACs need to be compared in constant
  time.  Use the appropriate helper function for this.
severity: critical
cvss: 9.4
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc <
    821c8751fdeecdeecabeb11704dd33439c9e4bbc
  - >-
    Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc <
    ff44ec94d4fc8348600a69de0a8fa1102c23bce8
  - >-
    Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc <
    345a9530756528d7ca407663d659c3c40e75c3dd
  - >-
    Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc <
    5d305a95130a8d08b9545e47f1e18d29d59866cb
  - >-
    Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc <
    02669e2a4d207068edce7e8b5fafd85822018ce6
  - >-
    Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc <
    ae3831b44f477de048287493e184fc3ff913b624
  - >-
    Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc <
    b502e97e29d791ff7a8051f29a414535739be218
  - >-
    Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc <
    46d0d6f50dab706637f4c18a470aac20a21900d3
  - Linux 2.6.20
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-16T15:16:58.789451Z'
published: '2026-05-08'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:20:40.656Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-43383'
references:
  - url: 'https://git.kernel.org/stable/c/821c8751fdeecdeecabeb11704dd33439c9e4bbc'
  - url: 'https://git.kernel.org/stable/c/ff44ec94d4fc8348600a69de0a8fa1102c23bce8'
  - url: 'https://git.kernel.org/stable/c/345a9530756528d7ca407663d659c3c40e75c3dd'
  - url: 'https://git.kernel.org/stable/c/5d305a95130a8d08b9545e47f1e18d29d59866cb'
  - url: 'https://git.kernel.org/stable/c/02669e2a4d207068edce7e8b5fafd85822018ce6'
  - url: 'https://git.kernel.org/stable/c/ae3831b44f477de048287493e184fc3ff913b624'
  - url: 'https://git.kernel.org/stable/c/b502e97e29d791ff7a8051f29a414535739be218'
  - url: 'https://git.kernel.org/stable/c/46d0d6f50dab706637f4c18a470aac20a21900d3'
tags:
  - cve.org
epss: 0.00443
epssPercentile: 0.37053
ingestedAt: '2026-10-16T17:24:46.694Z'
---

## Overview

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

net/tcp-md5: Fix MAC comparison to be constant-time

To prevent timing attacks, MACs need to be compared in constant
time.  Use the appropriate helper function for this.

## Affected

- `Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc < 821c8751fdeecdeecabeb11704dd33439c9e4bbc`
- `Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc < ff44ec94d4fc8348600a69de0a8fa1102c23bce8`
- `Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc < 345a9530756528d7ca407663d659c3c40e75c3dd`
- `Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc < 5d305a95130a8d08b9545e47f1e18d29d59866cb`
- `Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc < 02669e2a4d207068edce7e8b5fafd85822018ce6`
- `Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc < ae3831b44f477de048287493e184fc3ff913b624`
- `Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc < b502e97e29d791ff7a8051f29a414535739be218`
- `Linux >= cfb6eeb4c860592edd123fdea908d23c6ad1c7dc < 46d0d6f50dab706637f4c18a470aac20a21900d3`
- `Linux 2.6.20`

## Remediation

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