CVE-2026-90153

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size

smb_check_perm_dacl() validates that the DACL fits inside the NT

security descriptor, but then bounds its two ACE walks by the

remaining NTSD length (acl_size) rather than the DACL's declared

size (pdacl_size).

When pdacl->size is smaller than the trailing NTSD buffer, bytes

after the declared DACL boundary - still inside the stored security

descriptor - are parsed as ACEs during access checks. A crafted

DACL can place an access-granting ACE beyond pdacl->size, and the

current code accepts it during SMB2_CREATE access validation, while

parse_dacl() and smb_inherit_dacl() stop at pdacl_size.

Bound both ACE walks by pdacl_size to match the DACL boundary

semantics used elsewhere in the server.

Validation:

- semantic KUnit harness shows the post-boundary ACE is selected

before the fix and rejected (EACCES) after it

- linux master (7.2-rc6), x86_64

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References