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VulnerabilityPublished Updated

CVE-2025-71085: Linux kernel · ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()

Affects Linux kernelSource GCVE Database

0
Authoritative record:CVE-2025-71085· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in 5.15.0-1103.110~20.04.1 : patch Linux kernel soon.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 23% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 5.15.0-1103.110~20.04.1, 5.15.0-1110.119~20.04.1, 5.15.0-1103.112~20.04.1 +74
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 13 Jan 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 25.10linuxpkg:deb/ubuntu/linux?arch=source&distro=questingOther threatsAffected
  • <6.17.0-22.22
Fixed in
  • 6.17.0-22.22
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1012.12
Fixed in
  • 6.17.0-1012.12
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1013.13
Fixed in
  • 6.17.0-1013.13
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threatsAffected
  • 6.17.0-1003.3 – 6.17.0-1017.17
10 affected builds
Fixed in–
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1012.12
Fixed in
  • 6.17.0-1012.12
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1011.11
Fixed in
  • 6.17.0-1011.11

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

AI-suggested

Official patches are available and should be applied to affected Linux kernel versions. The Ubuntu security advisory USN-8096-1 provides updates for linux-azure kernels addressing this issue. Users should update their systems to the fixed kernel versions. No additional mitigations are specified or required beyond applying the official fix.

Description

A vulnerability in the Linux kernel's IPv6 subsystem was resolved that could cause a kernel oops due to an integer cast error in the pskb_expand_head() function. This occurs when calipso_skbuff_setattr() passes a headroom value greater than INT_MAX to skb_cow(), triggering a BUG_ON condition. The issue is fixed by correcting the trigger condition to avoid passing negative headroom sizes. The vulnerability affects certain linux-azure kernel versions prior to specific 5.15.x releases. A proof-of-concept exploit using netlabelctl and crafted IPv6 packets is known. The issue has a CVSS score of 7.5 and is rated medium severity. Official patches are available from Ubuntu and other Linux kernel maintainers.

References

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