Improper access control in Linux kernel - CVE-2026-68166
Published: August 12, 2026
Vulnerability identifier: #VU142139
CSH Severity: Low
CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-68166
CWE-ID: CWE-284
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to inject chosen return addresses.
The vulnerability exists due to improper access control in userfaultfd registration for virtual memory areas when registering shadow stack or special VMAs. A local user can register a shadow stack VMA with userfaultfd and inject a page with chosen return addresses via UFFDIO_COPY to inject chosen return addresses.
The issue involves shadow stack VMAs, and special VMAs are also affected in cases where a driver implements vm_uffd_ops.
Affected software
Linux kernel
How to mitigate CVE-2026-68166
Install security update from vendor's repository.
Linux kernel - update to 7.0 rc3