SB2026072066 - Improper locking in Linux kernel netfs

Description

This security bulletin contains information about 1 vulnerability.

1) Improper locking (CVE-ID: CVE-2026-64156)

CWE-ID: CWE-667 - Improper Locking

CVSSv4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to improper lock handling in netfs_writeback_single() and afs_single_writepages() when processing writeback operations under lock contention with WB_SYNC_NONE. A local user can trigger writeback in a way that causes skipped writes to leave directory or link data improperly handled, resulting in a denial of service.

This issue is described as theoretical for directories because the afs_single_writepages() path serializes access with validate_lock.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/77bb293049d61e04c12b24ebbffafaf5ab36af90
• https://git.kernel.org/stable/c/9871938f99cc6cb266a77265491660e2375271f5
• https://git.kernel.org/stable/c/f91e10435c0dd37c48b1b25e6236284f656ddc0c