CVE-2026-64156 addresses a flaw in the Linux kernel's netfs and AFS subsystems where netfs_write_single() and afs_single_writepages() did not correctly handle skipped writes caused by lock contention and WB_SYNC_NONE flags. The fix ensures that if a write is skipped, netfs_write_single() returns 1 and afs_single_writepages() also skips accordingly, with the inode being re-marked to maintain proper state since the VFS may have cleared the mark. This vulnerability is mainly theoretical for directories due to serialization by the validate_lock in afs_single_writepages().

The vulnerability could lead to skipped writes in directory or link writepages, causing the inode to be incorrectly marked and potentially resulting in availability issues (denial of service). There is no impact on confidentiality or integrity. No known exploits are reported in the wild.

A fix has been implemented in the Linux kernel to address this issue. Since no specific patch links or vendor advisories are provided, users should update to the latest Linux kernel versions where this fix is included. Patch status is not yet confirmed in the provided data—check the official Linux kernel advisories or distributions for current remediation guidance.