---
id: CVE-2025-39702
title: 'ipv6: sr: Fix MAC comparison to be constant-time'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ipv6: sr: 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: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c <
    ff55a452d56490047f5233cc48c5d933f8586884
  - >-
    Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c <
    3b348c9c8d2ca2c67559ffd0e258ae7e1107d4f0
  - >-
    Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c <
    86b6d34717fe0570afce07ee79b8eeb40341f831
  - >-
    Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c <
    3ddd55cf19ed6cc62def5e3af10c2a9df1b861c3
  - >-
    Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c <
    b3967c493799e63f648e9c7b6cb063aa2aed04e7
  - >-
    Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c <
    f7878d47560d61e3f370aca3cebb8f42a55b990a
  - >-
    Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c <
    a458b2902115b26a25d67393b12ddd57d1216aaa
  - Linux 4.10
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-15T21:53:32.850738Z'
published: '2025-09-05'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T22:02:30.641Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-39702'
references:
  - url: 'https://git.kernel.org/stable/c/ff55a452d56490047f5233cc48c5d933f8586884'
  - url: 'https://git.kernel.org/stable/c/3b348c9c8d2ca2c67559ffd0e258ae7e1107d4f0'
  - url: 'https://git.kernel.org/stable/c/86b6d34717fe0570afce07ee79b8eeb40341f831'
  - url: 'https://git.kernel.org/stable/c/3ddd55cf19ed6cc62def5e3af10c2a9df1b861c3'
  - url: 'https://git.kernel.org/stable/c/b3967c493799e63f648e9c7b6cb063aa2aed04e7'
  - url: 'https://git.kernel.org/stable/c/f7878d47560d61e3f370aca3cebb8f42a55b990a'
  - url: 'https://git.kernel.org/stable/c/a458b2902115b26a25d67393b12ddd57d1216aaa'
tags:
  - cve.org
epss: 0.00432
epssPercentile: 0.37247
ingestedAt: '2026-10-15T22:48:25.521Z'
---

## Overview

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

ipv6: sr: 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 >= bf355b8d2c30a289232042cacc1cfaea4923936c < ff55a452d56490047f5233cc48c5d933f8586884`
- `Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c < 3b348c9c8d2ca2c67559ffd0e258ae7e1107d4f0`
- `Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c < 86b6d34717fe0570afce07ee79b8eeb40341f831`
- `Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c < 3ddd55cf19ed6cc62def5e3af10c2a9df1b861c3`
- `Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c < b3967c493799e63f648e9c7b6cb063aa2aed04e7`
- `Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c < f7878d47560d61e3f370aca3cebb8f42a55b990a`
- `Linux >= bf355b8d2c30a289232042cacc1cfaea4923936c < a458b2902115b26a25d67393b12ddd57d1216aaa`
- `Linux 4.10`

## Remediation

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