CVE-2026-97561 smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid
An untrusted SMB server can override local file ownership settings, bypassing forceuid/forcegid mount options and potentially leading to privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-97561?
CVE-2026-97561 is a vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-97561?
How do I fix CVE-2026-97561?
Apply the vendor's patch.
Is CVE-2026-97561 being exploited?
There is no known exploitation of CVE-2026-97561 in the wild and no public exploit code.
Sources
Also known as AZL-104867, BELL-CVE-2026-97561, DEBIAN-CVE-2026-97561, GHSA-vg8h-339p-69c7, UBUNTU-CVE-2026-97561.