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VulnerabilityPublished Updated

CVE-2026-31685: Linux kernel · netfilter: ip6t_eui64: reject invalid MAC header for all packets

Affects Linux kernelSource GCVE Database

0
Authoritative record:CVE-2026-31685· Critical 9.4

Not known to be exploited · CVSS 9.4 Critical · fixed in 4.4.0-1156.162 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score
9.4Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 4.4.0-1156.162, 4.4.0-283.317~14.04.1, 4.4.0-1126.133 +83
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 25 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: 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 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde@7.0.0-1008.8?arch=source&distro=resoluteOther threatsAffected
  • 7.0.0-1003.3 – 7.0.0-1008.8
4 affected builds
Fixed in–
Ubuntu 26.04 LTSlinux-nvidiapkg:deb/ubuntu/linux-nvidia@7.0.0-1006.6?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-1006.6
Fixed in
  • 7.0.0-1006.6
Ubuntu 25.10linuxpkg:deb/ubuntu/linux@6.17.0-40.40?arch=source&distro=questingOther threatsAffected
  • <6.17.0-40.40
Fixed in
  • 6.17.0-40.40
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws@6.17.0-1019.19?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1019.19
Fixed in
  • 6.17.0-1019.19
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure@6.17.0-1020.20?arch=source&distro=questingOther threatsAffected
  • 6.14.0-1004.4 – 6.17.0-1020.20
16 affected builds
Fixed in–
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde@6.17.0-1017.17?arch=source&distro=questingOther threatsAffected
  • 6.17.0-1003.3 – 6.17.0-1017.17
10 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available and has been released by vendors, including Ubuntu. Users should update their Linux kernel packages to the fixed versions listed in the Ubuntu advisories USN-8490-1 and USN-8491-1 and reboot their systems to apply the updates. Due to an ABI change, recompilation and reinstallation of third-party kernel modules may be required. Follow vendor instructions carefully to ensure full remediation.

Description

A vulnerability in the Linux kernel's netfilter subsystem (ip6t_eui64) allowed packets with invalid MAC headers to be processed improperly due to insufficient validation. Specifically, the function eui64_mt6() did not reject invalid MAC headers for packets where the fragment offset was zero, potentially leading to improper access of Ethernet header data. This flaw has been fixed by removing the condition that exempted packets with zero fragment offset from validation, ensuring all packets with invalid MAC headers are rejected before processing. The vulnerability affects multiple Linux kernel versions prior to certain patched releases. A patch is available and has been incorporated into updated kernel packages. Users should update and reboot to apply the fix.

References

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