smb/client: fix chown/chgrp with SMB3 POSIX Extensions
CVE-2026-64388 · published 25 Jul 2026
How serious is it
- Severity: high, CVSS score 7.8 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-64388?
Paste this prompt into Claude Code, Cursor or any AI coding tool: it runs a free Shippable scan of your project and fixes what it finds. Built with Lovable, Bolt or v0? Scan your live app. Or upload your package file.
Who is affected
- Linux Linux: b326614ea2159ea5c835d320f261d05d080cd201 to < 6825a45f6b8ef76b0ee32649ec3d6e39ca143a18, b326614ea2159ea5c835d320f261d05d080cd201 to < 27ead8c5418af6bfab711079fecb9414d78d4cae, b326614ea2159ea5c835d320f261d05d080cd201 to < 3eaec47518e126e6dcd1a48521d740278073f0ec, b326614ea2159ea5c835d320f261d05d080cd201 to < 550cfb8a81181331d4d0f76ab75ee58a0bf41e3e
- Linux Linux: 4.18
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
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.
Check your whole app
Dependencies are only half of it. Free and read-only: before you push, run npx shippable-dev scan localhost:3000 in your project folder, no account needed. For your live app, you prove it's yours with a one-line tag first.
References
- git.kernel.org/stable/c/6825a45f6b8ef76b0ee32649ec3d6e39ca143a18
- git.kernel.org/stable/c/27ead8c5418af6bfab711079fecb9414d78d4cae
- git.kernel.org/stable/c/3eaec47518e126e6dcd1a48521d740278073f0ec
- git.kernel.org/stable/c/550cfb8a81181331d4d0f76ab75ee58a0bf41e3e
- git.kernel.org/stable/c/760ef2c579c2609cf17fb1cd5392f64d42d43d33
Merged from CVE List. Last updated 25 Oct 2026. All vulnerabilities · RSS · JSON