CVE-2026-43364: Linux kernel · ublk: fix NULL pointer dereference in ublk_ctrl_set_size()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium.
Data as of 26 Oct 2026, 12:55 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?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 adds proper NULL pointer checks in the ublk_ctrl_set_size() function. Users should apply the official kernel updates that address this issue. Since this is a kernel-level vulnerability, updating to patched kernel versions is the recommended remediation.
Description
A vulnerability in the Linux kernel's ublk subsystem allows a NULL pointer dereference in the ublk_ctrl_set_size() function. This occurs because the function dereferences a pointer without checking if it is NULL, which can happen if an UPDATE_SIZE command is sent to a device that is added but not started or has been stopped. This issue has been fixed by adding a check for the pointer under a mutex and returning an error if the disk is not available.
References
- ubuntu.com/security/CVE-2026-43364 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-43364 (opens in a new tab)
- git.kernel.org/linus/25966fc097691e5c925ad080f64a2f19c5fd940a (opens in a new tab)
- git.kernel.org/stable/c/25966fc097691e5c925ad080f64a2f19c5fd940a (opens in a new tab)
- git.kernel.org/stable/c/c28d945bfa92e15147e93b73f95345b9bec979b0 (opens in a new tab)
- git.kernel.org/stable/c/f13fe6794726755a43090cb680c4c58cea6aa5f1 (opens in a new tab)