Improper Preservation of Permissions in Linux kernel - CVE-2026-89638
Published: September 12, 2026
Vulnerability identifier: #VU149167
CSH Severity: Low
CVSS v4: 8.5 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-89638
CWE-ID: CWE-281
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to escalate privileges.
The vulnerability exists due to improper preservation of permissions in the cifs_setattr_unix() and cifs_setattr_nounix() routines when processing writes to files with setuid or setgid bits set. A local user can write to such a file and retain its setuid or setgid bits on the server to escalate privileges.
The issue occurs when the mount stores modes on the server through cifsacl or modefromsid, SMB3.1.1 POSIX extensions, or SMB1 Unix extensions.
Affected software
Linux kernel
How to mitigate CVE-2026-89638
Install security update from vendor's repository.