CVE-2026-97561
UnknownSummary
In the Linux kernel SMB client, several code paths unconditionally called sid_to_id(), overwriting cf_uid/cf_gid with server-provided values despite mounts using forceuid/forcegid options. This affected smb311_posix_info_to_fattr(), cifs_posix_to_fattr(), and parse_sec_desc(). It allowed an untrusted server to dictate local file ownership against the administrator's explicit configuration.
Risk Assessment
An untrusted SMB server can enforce file ownership contrary to the administrator's intent, potentially leading to incorrect access permissions and unauthorized data disclosure or modification. The issue affects mounts using forceuid/forcegid options.
Recommendation
Update the Linux kernel to a version containing the fix that checks CIFS_MOUNT_OVERR_UID and CIFS_MOUNT_OVERR_GID before calling sid_to_id(). Verify file ownership correctness on existing forceuid/forcegid mounts.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid When the administrator mounts with forceuid or forcegid (uid=/gid= mount options), they expect all files to appear owned by the specified user/group. However, several code paths unconditionally called sid_to_id() to overwrite cf_uid/cf_gid with server-provided values, ignoring the administrator's explicit override: - smb311_posix_info_to_fattr() (stat via POSIX extensions) - cifs_posix_to_fattr() (readdir via POSIX extensions) - parse_sec_desc() (CIFS ACL ownership mapping) This allowed an untrusted server to dictate local file ownership even when the mount was configured to force specific uid/gid values. Fix all three call sites to check CIFS_MOUNT_OVERR_UID and CIFS_MOUNT_OVERR_GID before calling sid_to_id(), following the same pattern already used by cifs_unix_basic_to_fattr() for unix extensions.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS