CVE-2026-43490

About vulnerability

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. A flaw was found in ksmbd, a Linux kernel module that provides an in-kernel Server Message Block (SMB) server. A remote attacker could exploit this vulnerability by providing a malformed inheritable Access Control Entry (ACE) within a security descriptor. This could lead to an out-of-bounds read or write operation, potentially causing a denial of service (DoS) or information disclosure. The flaw occurs because the system does not properly validate the length of the Security Identifier (SID) within the ACE during inheritance.

Live-patch status from KernelCare for each operating system.