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UBUNTU-CVE-2026-43490

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UBUNTU-CVE-2026-43490

Published: 15 May 2026Last Modified: 7 Sept 2026

Upstream:

Aliases:

Summary:

Details: In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate inherited ACE SID length smb_inherit_dacl() walks the parent directory DACL loaded from the security descriptor xattr. It verifies that each ACE contains the fixed SID header before using it, but does not verify that the variable-length SID described by sid.num_subauth is fully contained in the ACE. A malformed inheritable ACE can advertise more subauthorities than are present in the ACE. compare_sids() may then read past the ACE. smb_set_ace() also clamps the copied destination SID, but used the unchecked source SID count to compute the inherited ACE size. That could advance the temporary inherited ACE buffer pointer and nt_size accounting past the allocated buffer. Fix this by validating the parent ACE SID count and SID length before using the SID during inheritance. Compute the inherited ACE size from the copied SID so the size matches the bounded destination SID. Reject the inherited DACL if size accumulation would overflow smb_acl.size or the security descriptor allocation size.

Affected packages

Package

Name: linux-hwe-edge

Purl: pkg:deb/ubuntu/linux-hwe-edge?arch=source&distro=xenial

Affected ranges

Type: ECOSYSTEM

Events:

Introduced- 0

Fixed -None

Affected versions

4.8.0-28.30~16.04.1

4.8.0-30.32~16.04.1

4.8.0-32.34~16.04.1

4.8.0-34.36~16.04.1

Common Vulnerability Scoring System

Attack Vector

Network

Adjacent

Local

Physical

Privileges Required

None

Low

High

User Interaction

None

Required

Scope

Unchanged

Changed

Confidentiality

None

Low

High

Integrity

None

Low

High

Availability

None

Low

High