SB20260812368 - Improper access control in Linux kernel mm

Description

This security bulletin contains information about 1 vulnerability.

1) Improper access control (CVE-ID: CVE-2026-68166)

CWE-ID: CWE-284 - Improper Access Control

CVSSv4: 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]

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.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/0c26202b157f1efc3cd2f26f5c30f59b508a6a5d
• https://git.kernel.org/stable/c/165613191ad9d034bf17c00e3a142f9561597ec5
• https://git.kernel.org/stable/c/3c58f641e813c3c71039f8fd4d4e2a3aab713288