CVE-2026-64388

Retained file access via skipped ownership updates

Published Jul 25, 2026 · Updated Jul 25, 2026

Improper ownership handling in Linux Kernel 4.18 through 7.1.3 allows local users to retain access after chown or chgrp on SMB3 POSIX shares. In cifs_setattr_nounix(), the client skips id_mode_to_cifs_acl() when updating UID or GID unless CIFS ACL or SID-based mode flags are set, even when SMB3 POSIX extensions are active. The path requires a local call on an already mounted affected share; the prior owner or group can retain read, modification, and deletion rights after an apparent ownership transfer.

CVSS severity7.8
High
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper ownership handling in Linux Kernel 4.18 through 7.1.3 allows local users to retain access after chown or chgrp on SMB3 POSIX shares. In cifs_setattr_nounix(), the client skips id_mode_to_cifs_acl() when updating UID or GID unless CIFS ACL or SID-based mode flags are set, even when SMB3 POSIX extensions are active. The path requires a local call on an already mounted affected share; the prior owner or group can retain read, modification, and deletion rights after an apparent ownership transfer.

The record

CVE
CVE-2026-64388
Published
Jul 25, 2026
Updated
Jul 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1565.001
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <7.1.4
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <550cfb8a81181331d4d0f76ab75ee58a0bf41e3e
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <760ef2c579c2609cf17fb1cd5392f64d42d43d33

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=0 <7.1.4; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <550cfb8a81181331d4d0f76ab75ee58a0bf41e3e; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <760ef2c579c2609cf17fb1cd5392f64d42d43d33

Published CVSS scores

7.8LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.4Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1565.001Data Manipulation: Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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