Improper access control in Linux kernel - CVE-2026-64398

CSH
CYBERSECURITY HELP
Sign In REGISTER
 
Main Vulnerability Database Vulnerabilities #VU139568

Improper access control in Linux kernel - CVE-2026-64398

Published: July 27, 2026


Vulnerability identifier: #VU139568
CSH Severity: Medium
CVSS v4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-64398
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote user to modify file data without the required file write permission.

The vulnerability exists due to improper access control in smb2_ioctl() when processing FSCTL_SET_ZERO_DATA requests. A remote user can use a handle opened with only FILE_WRITE_ATTRIBUTES to zero file data and modify file contents without the required FILE_WRITE_DATA right.

The issue affects ksmbd, and the advisory states it was reproduced by an authenticated SMB client using a handle that was granted FILE_WRITE_ATTRIBUTES but not FILE_WRITE_DATA.


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-2026-64398

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