SB20261023189 - Incorrect authorization in Linux kernel fs

Description

This security bulletin contains information about 1 vulnerability.

1) Incorrect authorization (CVE-ID: CVE-2026-98978)

CWE-ID: CWE-863 - Incorrect Authorization

CVSSv4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a local user to disclose files and directories concealed by locked mounts.

The vulnerability exists due to improper enforcement of mount locking in shrink_submount() in fs/namespace.c when reclaiming shrinkable mounts during unmount operations. A local user can place a shrinkable mount beneath a locked mount using MOVE_MOUNT_BENEATH in a user namespace they own, then unmount an unlocked ancestor to expose the covered directory and read otherwise hidden files.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/6b8dc3713a76346d212abab46cbfc8d7070f534c
• https://git.kernel.org/stable/c/d23265a12e4991ce7aedce670c0b6b598cadb644
• https://git.kernel.org/stable/c/f78ddcc872248c7aa1d7e904928441a0be4c6d5d