CVE-2025-40100: Linux kernel · btrfs: do not assert we found block group item when creating free space tree
Affects Linux kernelSource GCVE Database
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
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
Disclosed: evidence found.
CVE published 30 Oct 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linuxpkg:deb/ubuntu/linux@6.17.0-14.14?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws@6.17.0-1007.7?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure@6.17.0-1008.8?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde@6.17.0-1017.17?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp@6.17.0-1007.7?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle@6.17.0-1007.7?arch=source&distro=questingOther threats | Affected
| Fixed in
|
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
- ubuntu.com/security/CVE-2025-40100 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-40100 (opens in a new tab)
- git.kernel.org/linus/a5a51bf4e9b7354ce7cd697e610d72c1b33fd949 (opens in a new tab)
- git.kernel.org/stable/c/289498da343b05c886f19b4269429606f86dd17b (opens in a new tab)
- git.kernel.org/stable/c/3fdcfd91b93f930d87843156c7c8cc5fbcf9b144 (opens in a new tab)
- git.kernel.org/stable/c/4f4b9ca73f84130d9fbb0fc02306ce94ce8bdbe6 (opens in a new tab)
- git.kernel.org/stable/c/a5a51bf4e9b7354ce7cd697e610d72c1b33fd949 (opens in a new tab)
- git.kernel.org/stable/c/eb145463f22d7d32d426b29fe9810de9e792b6ba (opens in a new tab)
- ubuntu.com/security/notices/USN-8029-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8030-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8029-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8048-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8029-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8095-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8100-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8095-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8095-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8095-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8125-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8126-1 (opens in a new tab)