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VulnerabilityPublished Updated

CVE-2025-40100: Linux kernel · btrfs: do not assert we found block group item when creating free space tree

Affects Linux kernelSource GCVE Database

0

Not known to be exploited · fixed in 6.8.0-1050.53~22.04.1 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 09:15 UTC

Severity
Medium

Rated by Threat Radar · No CVSS score from NVD or the CNA

EPSS
0.2% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 6.8.0-1050.53~22.04.1, 6.8.0-1051.57~22.04.1, 6.8.0-1052.55~22.04.1 +35

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 30 Oct 2025

  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@6.17.0-14.14?arch=source&distro=questingOther threatsAffected
  • <6.17.0-14.14
Fixed in
  • 6.17.0-14.14
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws@6.17.0-1007.7?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1007.7
Fixed in
  • 6.17.0-1007.7
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure@6.17.0-1008.8?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1008.8
Fixed in
  • 6.17.0-1008.8
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–
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp@6.17.0-1007.7?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1007.7
Fixed in
  • 6.17.0-1007.7
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle@6.17.0-1007.7?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1007.7
Fixed in
  • 6.17.0-1007.7

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

AI-suggested

An official patch is available and should be applied to affected Linux Azure kernel versions. The vendor advisory from Ubuntu confirms that this and other kernel vulnerabilities have been fixed in updated kernel packages. Users should update their systems to the fixed kernel versions as per the vendor's security notices.

Description

A vulnerability in the Linux kernel's Btrfs filesystem code was resolved, involving an incorrect assertion during free space tree creation. The issue occurs when a new block group is created but its item is not yet added to the extent tree, causing a kernel BUG due to an invalid assertion. This flaw was reported by Syzbot and affects specific Linux Azure kernel versions. A patch is available that removes the faulty assertion and updates the code comments accordingly.

References

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