Executive brief
A vulnerability in the Linux kernel's SMB client could prevent file ownership and group changes from being correctly applied to a server. When using specific SMB3 POSIX extensions, requests to change file owners or groups were silently ignored by the system. This could lead to incorrect file permissions and access control issues on shared network storage.
Technical details
A logic error in the Linux kernel's SMB client (cifs.ko) caused ownership (chown) and group (chgrp) modifications to be ignored when a share was mounted with SMB3 POSIX Extensions. The vulnerability existed in cifs_setattr_nounix(), where the code failed to check for posix_extensions before attempting to map UIDs and GIDs to the server. This resulted in the id_mode_to_cifs_acl() function not being called to synchronize ownership metadata unless CIFS_MOUNT_CIFS_ACL or CIFS_MOUNT_MODE_FROM_SID were explicitly enabled. The fix ensures that posix_extensions are checked during attribute updates to correctly map and set ownership information on the server.
Affected products
- Linux Linux Kernel 7.1.4, 7.2-rc1
Timeline
- 2026-06-07: other: Patch authored
- 2026-07-25: disclosed: CVE published