Bug 2540469 (CVE-2026-93786)

Summary: CVE-2026-93786 kernel: ksmbd: preserve VFS inherited POSIX ACL mask
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's ksmbd (in-kernel Server Message Block) component. When creating new files or directories, ksmbd improperly modified inherited Access Control Lists (ACLs) by overwriting restrictive permission masks. An authenticated user creating objects on an SMB share could exploit this flaw to widen effective file permissions, potentially leading to unauthorized access to files and directories.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2026-09-24 16:56:29 UTC
In the Linux kernel, the following vulnerability has been resolved:

ksmbd: preserve VFS inherited POSIX ACL mask

The VFS initializes a child's POSIX ACL from the parent's default ACL and
the requested creation mode. Do not mutate the parent ACL or overwrite the
child's VFS-computed access and default ACLs afterwards.

This preserves restrictive ACL_MASK entries and prevents SMB object creation
from widening effective permissions.