CVE-2026-93786

Received Received - Intake

ksmbd ACL Mask Preservation Vulnerability

Publication date: 2026-09-24

Last updated on: 2026-10-03

Assigner: kernel.org

Description

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-24

Last Modified

2026-10-03

Generated

2026-10-15

AI Q&A

2026-09-24

EPSS Evaluated

2026-10-13

NVD

CVE-2026-93786

EUVD

EUVD-2026-86173

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves improper handling of POSIX ACLs (Access Control Lists) in the ksmbd component. When creating a new SMB object, the kernel incorrectly modifies the parent ACL or overwrites the child's computed ACLs, potentially allowing wider permissions than intended. The fix ensures the child's ACL inherits restrictive permissions from the parent without mutation.

Detection Guidance

This vulnerability is specific to the Linux kernel's ksmbd implementation and relates to POSIX ACL handling. Detection requires checking if your system is running a vulnerable kernel version. Use uname -a to check the kernel version and verify if it matches affected releases.

Impact Analysis

If exploited, this flaw could allow unauthorized users to gain elevated access to files or directories shared via SMB, bypassing intended permission restrictions. Attackers might create or modify files with unintended permissions, leading to data leaks or unauthorized system access.

Compliance Impact

This vulnerability could violate compliance requirements that mandate strict access controls, such as GDPR's data protection principles or HIPAA's safeguards for protected health information. Unauthorized access risks may lead to regulatory penalties or data breaches.

Mitigation Strategies

Update the Linux kernel to a patched version that resolves the ksmbd ACL mask issue. Monitor vendor advisories for kernel updates addressing this CVE. Disable ksmbd if not needed until patched.

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