CVE-2026-43299: Linux kernel · btrfs: do not ASSERT() when the fs flips RO inside btrfs_repair_io_failure()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium.
Data as of 26 Oct 2026, 13:47 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 8 May 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 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde@7.0.0-1008.8?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 25.10linuxpkg:deb/ubuntu/linux?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp?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
A fix has been implemented that replaces the ASSERT() with a proper return when the filesystem is already read-only, preventing the kernel crash. Users should apply the official kernel updates that include this fix. Patch status is not explicitly stated in the input data; check the vendor advisory for current remediation guidance.
Description
A vulnerability in the Linux kernel's Btrfs filesystem code caused a kernel crash when the filesystem flipped to read-only mode during a read-repair operation after encountering an ENOSPC error. This was due to an ASSERT() check that failed if the filesystem was read-only, leading to a kernel BUG. The issue has been fixed by replacing the ASSERT() with a proper return when the filesystem is already read-only.
References
- ubuntu.com/security/CVE-2026-43299 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-43299 (opens in a new tab)
- git.kernel.org/linus/8ceaad6cd6e7fa5f73b0b2796a2e85d75d37e9f3 (opens in a new tab)
- git.kernel.org/stable/c/8ceaad6cd6e7fa5f73b0b2796a2e85d75d37e9f3 (opens in a new tab)
- git.kernel.org/stable/c/f6df18c001e3dcebc08482d0adeacd0cfea08593 (opens in a new tab)