What’s Vulnerable › Vulnerabilities

CVE-2026-64388: smb/client: fix chown/chgrp with SMB3 POSIX Extensions

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-25 · updated 2026-10-30
• Weakness: CWE-682

Description

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.

Affected products

• Linux kernel: from 4.18 before 7.1.4 — fixed in 7.1.4
• Linux: 4.18 — fixed in 7.2

How to fix

Upgrade to a fixed version: Linux kernel 7.1.4; Linux 7.2. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/27ead8c5418af6bfab711079fecb9414d78d4cae
• https://git.kernel.org/stable/c/3eaec47518e126e6dcd1a48521d740278073f0ec
• https://git.kernel.org/stable/c/550cfb8a81181331d4d0f76ab75ee58a0bf41e3e
• https://git.kernel.org/stable/c/6825a45f6b8ef76b0ee32649ec3d6e39ca143a18
• https://git.kernel.org/stable/c/760ef2c579c2609cf17fb1cd5392f64d42d43d33
• https://git.kernel.org/stable/c/c0fe1118a1471d459f76c3e70ff2abbf784ce6bf

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