CVE-2026-99063: Linux kernel · dm ioctl: don't let data_start run past the buffer
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 28 Oct 2026, 01:42 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
Exploitation evidence
Disclosed: evidence found.
CVE published 23 Oct 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 26.10linuxpkg:deb/ubuntu/linux?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=stonkingOther 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 clamps the data_start pointer to the actual buffer size, preventing the out-of-bounds read. Users should apply the updated Linux kernel versions that include this patch. Since exploitation requires root privileges, restricting root access and applying the official kernel updates are the recommended mitigations.
Description
CVE-2026-99063 is a Linux kernel vulnerability in the device mapper ioctl interface where a buffer over-read can occur due to improper bounds checking of the data_start pointer relative to the buffer size. This flaw can cause a small out-of-bounds read of up to seven bytes past the allocated buffer. The issue arises because the struct dm_ioctl has trailing padding, and the kernel code does not clamp data_start to the actual buffer size. The vulnerability can only be triggered by root privileges and has been fixed by clamping data_start to the buffer size.
References
- ubuntu.com/security/CVE-2026-99063 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-99063 (opens in a new tab)
- git.kernel.org/stable/c/5680b6fb3054677d4ee65d3baba24b649f1b430e (opens in a new tab)
- git.kernel.org/stable/c/725b49c689bbb29ef740b0d6b5ea9390baa9a695 (opens in a new tab)
- git.kernel.org/stable/c/98195e822343a656b92e235847ab3e72b1a3f920 (opens in a new tab)
- git.kernel.org/stable/c/9b3fcf519d370df94a56f3b272d9eddffffa5be8 (opens in a new tab)
- git.kernel.org/stable/c/e5c3f3d8935ecc64c962fb66e6a86dbf79218f61 (opens in a new tab)