CVE-2026-89638 Linux Kernel - Broken Access Control

Linux kernel contains a broken access control vulnerability caused by improper clearing of setuid/setgid bits on write with cifsacl/modefromsid/posix extensions, letting attackers retain setuid/setgid bits unexpectedly, exploit requires usage of affected CIFS mount options.

CVSS base score 7.8 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Required
EPSS
0.17% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Broken Access Control
Impact
Privilege Escalation
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published
11 September 2026
Updated
15 October 2026

Vendor fix

Update to the latest Linux kernel version containing the fix for proper clearing of setuid/setgid bits on CIFS mounts.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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