Linux Kernel smb/client cifs_setattr_nounix privileges management

Summaryinfo

A vulnerability marked as very critical has been reported in Linux Kernel. This impacts the function cifs_setattr_nounix of the component smb/client. Performing a manipulation results in privileges management. This vulnerability is known as CVE-2026-64388. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability, which was classified as very critical, was found in Linux Kernel (the affected version is unknown). This affects the function cifs_setattr_nounix 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. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: smb/client: fix chown/chgrp with SMB3 POSIX Extensions Ownership (chown) and group (chgrp) modifications were being ignored when mounting with SMB3 POSIX Extensions unless CIFS_MOUNT_CIFS_ACL or CIFS_MOUNT_MODE_FROM_SID were also explicitly set. Fix this by checking for posix_extensions in cifs_setattr_nounix() when updating UID and GID, ensuring that id_mode_to_cifs_acl() is called to map and set the ownership/group information on the server.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-64388 since 07/19/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details are known, but no exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 07/25/2026). MITRE ATT&CK project uses the attack technique T1068 for this issue.

Applying the patch 550cfb8a81181331d4d0f76ab75ee58a0bf41e3e is able to eliminate this problem.

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

License

• open-source

Website

• Vendor: https://www.kernel.org/

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