Linux Kernel up to 7.2.6/7.3-rc2 SMB Client privileges management

Summaryinfo

A vulnerability classified as very critical was found in Linux Kernel up to 7.2.6/7.3-rc2. Affected is the function smb311_posix_info_to_fattr/cifs_posix_to_fattr/parse_sec_desc of the component SMB Client. The manipulation results in privileges management. This vulnerability is identified as CVE-2026-97561. The attack can be executed remotely. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.6/7.3-rc2. It has been classified as very critical. Affected is the function smb311_posix_info_to_fattr/cifs_posix_to_fattr/parse_sec_desc of the component SMB Client. The manipulation with an unknown input leads to a privileges management vulnerability. CWE is classifying the issue as CWE-269. The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at git.kernel.org. This vulnerability is traded as CVE-2026-97561 since 09/24/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation needs additional levels of successful authentication. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/25/2026). This vulnerability is assigned to T1068 by the MITRE ATT&CK project.

Upgrading to version 7.2.7 or 7.3-rc3 eliminates this vulnerability. Applying the patch e1b74f8f8c1d13190b09fe623b729d36b7ac22a8/18a72975e9f35aadecc75b031f693f2d1f49308f is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.3-rc1
• 7.3-rc2

License

• open-source

Website

• Vendor: https://www.kernel.org/

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