CVE-2026-64388 (GCVE-0-2026-64388)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:50 – Updated: 2026-08-05 12:41
VLAI
Title
smb/client: fix chown/chgrp with SMB3 POSIX Extensions
Summary
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.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: b326614ea2159ea5c835d320f261d05d080cd201 , < 550cfb8a81181331d4d0f76ab75ee58a0bf41e3e (git)
Affected: b326614ea2159ea5c835d320f261d05d080cd201 , < 760ef2c579c2609cf17fb1cd5392f64d42d43d33 (git)
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Linux Linux Affected: 4.18
Unaffected: 0 , < 4.18 (semver)
Unaffected: 7.1.4 , ≤ 7.1.* (semver)
Unaffected: 7.2-rc1 , ≤ * (original_commit_for_fix)
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              "value": "AV:L - The vulnerable branch is reached through local chown/chgrp syscalls on an already mounted SMB3 POSIX share; unsolicited SMB traffic cannot invoke it.\nAC:L - With the affected mount configuration, the client deterministically skips the ownership update and returns success; no race, heap layout, or uncontrollable timing is required.\nPR:L - A basic local user can exercise the path on accessible share objects, and noperm deliberately defers authorization to the server whose ownership check is bypassed because no request is sent. The attacker need not create the mount.\nUI:N - The attacker can invoke the syscall directly and exploit continued rights or falsely cached ownership through automated services without human action.\nS:U - The defect affects resources governed through the vulnerable kernel and mounted share without escaping a VM, sandbox, or other distinct security authority.\nC:H - Because the intended ownership change never reaches the server, the prior owner or group can retain read access to an entire data tree believed to have been transferred or revoked.\nI:H - The prior owner can retain arbitrary modification rights, while falsely cached privileged ownership can cause privileged consumers to trust or execute attacker-controlled content.\nA:H - Retained ownership of writable files or directories can permit truncation or deletion of an entire service data tree, and privileged execution through false ownership can cause a complete outage."
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    "datePublished": "2026-07-25T08:50:36.202Z",
    "dateReserved": "2026-07-19T15:36:31.784Z",
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}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.