SB20261023180 - Incorrect Synchronization in Linux kernel fs

Description

This security bulletin contains information about 1 vulnerability.

1) Incorrect Synchronization (CVE-ID: CVE-2026-98986)

CWE-ID: CWE-821 - Incorrect Synchronization

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

The vulnerability allows a local user to potentially cause a denial of service through invalid kernel locking during mount namespace destruction.

The vulnerability exists due to improper synchronization in mount namespace cleanup when fanotify marks are removed from RCU softirq context, where acquiring a mutex can sleep. A local user can use root privileges within a user namespace to place a FAN_MARK_MNTNS mark on another task's mount namespace that the user namespace owns and trigger cleanup when that task exits to potentially cause a denial of service.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/1a116222acdcc1bc1a8350727ae6f28907d44594
• https://git.kernel.org/stable/c/888363d74c3b5d32e2accf217add70f8b38e0e2b
• https://git.kernel.org/stable/c/9e820a6becdd955a04adbedfd767253a47eedd9e