CVE-2026-97561
Received Received - Intake

SMB Client Forceuid Forcegid Ownership Bypass

Publication date: 2026-09-25

Last updated on: 2026-09-25

Assigner: kernel.org

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.

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Meta Information

Published
2026-09-25
Last Modified
2026-09-25
Generated
2026-09-25
AI Q&A
2026-09-25
EPSS Evaluated
N/A
NVD
CVE-2026-97561
EUVD
EUVD-2026-86869

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel allows a malicious SMB server to override local file ownership settings when a client mounts a share with forceuid or forcegid options. Normally, these options force all files to appear owned by a specified user or group, but certain code paths ignored these settings and used server-provided values instead.

Impact Analysis

If you mount an SMB share with forceuid or forcegid, an untrusted server could manipulate file ownership, potentially allowing unauthorized access to sensitive files or causing system instability by altering ownership of critical files.

Compliance Impact

This vulnerability could lead to unauthorized access or modification of sensitive data, violating compliance requirements like GDPR (data protection) or HIPAA (health information privacy) by allowing improper file ownership changes.

Mitigation Strategies

Update the Linux kernel to the latest patched version to resolve the vulnerability. Ensure that the forceuid and forcegid mount options are properly enforced by verifying the kernel behavior after update.

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