CVE-2026-93800: Linux kernel · btrfs: fix use-after-free on reloc root after error in insert_dirty_subvol()
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 26 Oct 2026, 17:16 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Exploitation evidence
Disclosed: evidence found.
CVE published 24 Sep 2026
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
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther 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
A fix for this vulnerability has been implemented in the Linux kernel. Users should apply the official kernel updates that address this issue. Since this is a kernel-level bug, upgrading to a patched kernel version is the recommended remediation. Patch status is confirmed by the advisory stating the vulnerability has been resolved. No additional mitigations are indicated.
Description
A use-after-free vulnerability in the Linux kernel's Btrfs filesystem was resolved. The flaw occurs when an error during relocation in insert_dirty_subvol() leads to a root's reloc_root field pointing to freed memory, causing a use-after-free or double free during unmount. This can trigger kernel memory corruption and instability. The issue was reported by Syzbot and results in transaction aborts and kernel warnings. Affected versions include specific Linux kernel builds from 3.11.0-12.19 through 3.13.0-8.28. The severity is medium due to potential kernel crashes but no known exploits in the wild. No CVSS score is available.
References
- ubuntu.com/security/CVE-2026-93800 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-93800 (opens in a new tab)
- git.kernel.org/stable/c/97a540d72ebcb21853d11f2a56782fe377f358e7 (opens in a new tab)
- git.kernel.org/stable/c/83201804efa4a5168be754e1dfc9b2faee760cac (opens in a new tab)
- git.kernel.org/stable/c/fda1b6636ff1846f00643e791099db5564b547d9 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-93800 (opens in a new tab)
- git.kernel.org/stable/c/5a247097c5f94b51ffc991b444d998ad6e85875f (opens in a new tab)
- git.kernel.org/stable/c/6372dd394ea907cd85a7a8063db320ec73dfaed0 (opens in a new tab)
- git.kernel.org/stable/c/9f599d120b2b79d2d937c3935b7cdf2697514283 (opens in a new tab)
- git.kernel.org/stable/c/a01837ae174a2a968c245a30e6dd010f50eaf05d (opens in a new tab)