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VulnerabilityPublished Updated

CVE-2025-39770: Linux kernel · net: gso: Forbid IPv6 TSO with extensions on devices with only IPV6_CSUM

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High · fixed in a0478d7e888028f85fa7785ea838ce0ca09398e2 : patch Linux kernel soon.

Data as of 10 Nov 2026, 12:49 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (Linux)CVSS 3.17.5
Patch
Available – fixed in a0478d7e888028f85fa7785ea838ce0ca09398e2, 2156d9e9f2e483c8c3906c0ea57ea312c1424235, 864e3396976ef41de6cc7bc366276bf4e084fff2 +9
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 11 Sep 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • >=6.1.116 <6.1.149
  • >=6.6.60 <6.6.103
  • >=4.19.323 <4.20
  • >=5.4.285 <5.5
  • >=5.10.229 <5.11
  • >=5.15.171 <5.16
  • >=6.11.7 <6.12
Fixed in
  • a0478d7e888028f85fa7785ea838ce0ca09398e2
  • 2156d9e9f2e483c8c3906c0ea57ea312c1424235
  • 864e3396976ef41de6cc7bc366276bf4e084fff2
  • 794ddbb7b63b6828c75967b9bcd43b086716e7a1
  • 041e2f945f82fdbd6fff577b79c33469430297aa
  • 6.12
  • 6.6.103
  • 6.1.149
  • 5.16
  • 5.11
  • 5.5
  • 4.20
LinuxLinuxAffected
  • =6.12
Fixed in–

AI-suggested

A fix is available and has been applied in Linux kernel versions 4.20, 5.5, 5.11, 5.16, 6.1.149, 6.6.103, and 6.12. Users and administrators should upgrade to these or later kernel versions to resolve the issue. No additional mitigation steps are required beyond applying the official kernel updates.

Description

CVE-2025-39770 is a vulnerability in the Linux kernel's network stack involving Generic Segmentation Offload (GSO) for IPv6 packets with extension headers. The kernel incorrectly requests checksum offload on devices that only support IPV6_CSUM for plain TCP or UDP over IPv6, violating the device's contract. This leads to warnings and a collapse of network throughput. The issue has been fixed in multiple Linux kernel versions starting from 4.20, 5.5, 5.11, 5.16, 6.1.149, 6.6.103, and 6.12. The fix involves disabling checksum offload requests for packets with IPv6 extension headers and computing checksums in software instead.

References

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