The flaw lies in the Linux kernel’s CIFS client when handling SMB1 UNIX mounts. During the mount process, the cifs_mount_get_tcon() function may read or update the CIFS_MOUNT_POSIXACL and CIFS_MOUNT_POSIX_PATHS bits only after reset_cifs_unix_caps(), causing the CIFS_MOUNT_POSIX_PATHS flag to be missing. This omission leads to the use of an incorrect directory separator in paths. The weakness is a pathname handling problem (CWE‑22) and does not grant unauthorized file access, privilege escalation, or code execution. Its effect is limited to incorrect path resolution on mounted shares, which can affect functionality rather than security posture.

All Linux kernel releases before the patch containing the dir separator fix are affected. The issue resides in the CIFS SMB client component used by distributions that mount SMB shares using the CIFS helper. Any Linux system that relies on the unpatched kernel for SMB1 support is potentially impacted.

No EPSS score is available and the vulnerability is not listed in CISA’s KEV catalog, indicating a low likelihood of exploitation. There are no reported exploits. The bug manifests during client-initiated SMB mount operations, so a remote attacker could not exploit it without first mounting the share locally or having the affected client performed the mount. The flaw does not provide a direct vector for code execution or data exfiltration, and so the overall risk is low to moderate.