The Linux kernel incorrectly ignores chown and chgrp system calls on CIFS filesystems that are mounted with SMB3 POSIX Extensions unless the mount options CIFS_MOUNT_CIFS_ACL or CIFS_MOUNT_MODE_FROM_SID are explicitly set. This means that attempts by users to change the perceived ownership or group of a file on the remote share are not reflected in the server’s metadata. The flaw corresponds to CWE‑279, an authorization management weakness, and represents an authorization management defect rather than a privilege escalation path.

All Linux kernel installations that use CIFS mounts with SMB3 POSIX Extensions are affected, until the kernel commits referenced in the advisory are applied. No specific distribution versions are enumerated; the issue applies to any kernel version that includes the buggy code path for posix_extensions handling in cifs_setattr_nounix().

The CVSS score of this vulnerability is 7.8, indicating a high severity impact on integrity. The EPSS score is below 1 %, and the vulnerability is not listed in CISA KEV, pointing to a low likelihood of widespread exploitation. Because the bug merely prevents the user from propagating ownership changes, it does not provide a direct route to privilege escalation or remote code execution. The likely attack vector is a local attacker who can mount the affected SMB share and observe that ownership modifications are not applied, but this does not translate into a controllable attack.