CVE-2026-43308: Linux kernel · btrfs: don't BUG() on unexpected delayed ref type in run_one_delayed_ref()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 1% 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 is available that replaces the BUG() call with error handling and logging. Users should apply the official Linux kernel updates that include this fix. Since this is not a cloud service, remediation depends on patching the affected kernel versions.
Description
A vulnerability in the Linux kernel's Btrfs filesystem code caused the kernel to BUG() (crash) on encountering an unexpected delayed reference type in the run_one_delayed_ref() function. This behavior has been resolved by changing the code to return and log an error instead of crashing.
References
- ubuntu.com/security/CVE-2026-43308 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-43308 (opens in a new tab)
- git.kernel.org/linus/c7d1d4ff56744074e005771aff193b927392d51f (opens in a new tab)
- git.kernel.org/stable/c/5549743e11c06da23cfa7712a994b9f1e69064c6 (opens in a new tab)
- git.kernel.org/stable/c/c7d1d4ff56744074e005771aff193b927392d51f (opens in a new tab)