CVE Catalog

CVE-2026-43490

HighCVSS 8.8
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.41%

33th percentile - higher than 33% of all known CVEs

Summary

In the Linux kernel, the ksmbd filesystem has a vulnerability due to missing validation of SID length in inherited ACE entries. A malformed ACE can advertise more subauthorities than present, leading to out-of-bounds read by compare_sids() and potential buffer overflow when computing inherited ACE size.

Risk Assessment

An attacker could exploit this vulnerability to read out-of-bounds memory or cause a system crash (DoS) by supplying a crafted security descriptor.

Recommendation

Immediately update the Linux kernel to a version containing the fix that validates the SID subauthority count and SID length before use during ACE inheritance.

Related vulnerabilities

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS