Improper access control in Linux kernel - CVE-2026-64395

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Main Vulnerability Database Vulnerabilities #VU139582

Improper access control in Linux kernel - CVE-2026-64395

Published: July 27, 2026


Vulnerability identifier: #VU139582
CSH Severity: Medium
CVSS v4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-64395
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote user to disclose sensitive information.

The vulnerability exists due to improper access control in FSCTL_DUPLICATE_EXTENTS_TO_FILE handling in ksmbd when processing duplicate extents requests. A remote user can use a source handle opened without read access to copy file contents into an attacker-readable destination to disclose sensitive information.

The issue affects the source file access check before invoking file range clone or copy operations.


Affected software

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-lowlatency (Ubuntu package)
linux-raspi (Ubuntu package)
linux-azure (Ubuntu package)
linux-gcp (Ubuntu package)
linux-aws (Ubuntu package)
linux-ibm (Ubuntu package)
linux-oracle (Ubuntu package)
linux-azure-fde (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-realtime (Ubuntu package)
linux-hwe-6.8 (Ubuntu package)
linux-lowlatency-hwe-6.8 (Ubuntu package)
linux-fips (Ubuntu package)
linux-azure-fde-6.8 (Ubuntu package)
linux-oracle-6.8 (Ubuntu package)
linux-nvidia-tegra (Ubuntu package)
linux-aws-6.8 (Ubuntu package)
linux-azure-6.8 (Ubuntu package)
linux-nvidia-lowlatency (Ubuntu package)
linux-gkeop (Ubuntu package)
linux-gke (Ubuntu package)
linux-ibm-6.8 (Ubuntu package)
linux-gcp-6.8 (Ubuntu package)
linux-aws-fips (Ubuntu package)
linux-gcp-fips (Ubuntu package)
linux-azure-fips (Ubuntu package)
linux-raspi-realtime (Ubuntu package)
linux-realtime-6.8 (Ubuntu package)
linux-nvidia-bos (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-azure-7.0 (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux-oracle-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)
linux-aws-7.0 (Ubuntu package)
linux-nvidia-7.0 (Ubuntu package)

How to mitigate CVE-2026-64395

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - addressed in versions 6.8.0-147.147, 7.0.0-31.31
linux-lowlatency (Ubuntu package) - update to 6.8.0-147.147.1
linux-raspi (Ubuntu package) - addressed in versions 6.8.0-1068.72, 7.0.0-1019.19
linux-azure (Ubuntu package) - addressed in versions 6.8.0-1071.79, 7.0.0-1014.14
linux-gcp (Ubuntu package) - addressed in versions 6.8.0-1071.79, 7.0.0-1011.11
linux-aws (Ubuntu package) - addressed in versions 6.8.0-1067.70, 7.0.0-1012.12
linux-ibm (Ubuntu package) - addressed in versions 6.8.0-1067.68, 7.0.0-1013.13
linux-oracle (Ubuntu package) - addressed in versions 6.8.0-1064.67, 7.0.0-1011.11
linux-azure-fde (Ubuntu package) - update to 6.8.0-1069.76
linux-nvidia (Ubuntu package) - addressed in versions 6.8.0-1067.70, 7.0.0-1018.18
linux-realtime (Ubuntu package) - addressed in versions 6.8.1-1062.63, 7.0.0-31.31.1
linux-hwe-6.8 (Ubuntu package) - update to 6.8.0-149.149~22.04.1
linux-lowlatency-hwe-6.8 (Ubuntu package) - update to 6.8.0-149.149.1~22.04.1
linux-fips (Ubuntu package) - update to 6.8.0-147.147+fips1
linux-azure-fde-6.8 (Ubuntu package) - update to 6.8.0-1071.78~22.04.1
linux-oracle-6.8 (Ubuntu package) - update to 6.8.0-1067.71~22.04.1
linux-nvidia-tegra (Ubuntu package) - update to 6.8.0-1036.39
linux-aws-6.8 (Ubuntu package) - update to 6.8.0-1069.74~22.04.1
linux-azure-6.8 (Ubuntu package) - update to 6.8.0-1073.82~22.04.1
linux-nvidia-lowlatency (Ubuntu package) - update to 6.8.0-1067.70.1
linux-gkeop (Ubuntu package) - update to 6.8.0-1052.56
linux-gke (Ubuntu package) - addressed in versions 6.8.0-1066.74, 7.0.0-1006.7
linux-ibm-6.8 (Ubuntu package) - update to 6.8.0-1069.70~22.04.1
linux-gcp-6.8 (Ubuntu package) - update to 6.8.0-1073.81~22.04.1
linux-aws-fips (Ubuntu package) - update to 6.8.0-1067.70+fips1
linux-gcp-fips (Ubuntu package) - update to 6.8.0-1071.79+fips1
linux-azure-fips (Ubuntu package) - update to 6.8.0-1071.79+fips1
linux-raspi-realtime (Ubuntu package) - update to 6.8.0-2056.58
linux-realtime-6.8 (Ubuntu package) - update to 6.8.1-1064.65~22.04.1
linux-nvidia-bos (Ubuntu package) - update to 7.0.0-2018.18
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-31.31~24.04.1
linux-azure-7.0 (Ubuntu package) - update to 7.0.0-1014.14~24.04.1
linux-gcp-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-oracle-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1013.13
linux-aws-7.0 (Ubuntu package) - update to 7.0.0-1012.12~24.04.1
linux-nvidia-7.0 (Ubuntu package) - update to 7.0.0-1018.18~24.04.1

External References

Related Security Bulletins