ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size

Summary

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

Timeline

1. Sep 17, 2026, 4:06 PM UTCCVE published
2. Oct 19, 2026, 8:58 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 8f0541186e9ad1b62accc9519cc2b7a7240272a7 · fixed in a2051ffe452afad52f580b85a3fd8851933b1e7c; From 8f0541186e9ad1b62accc9519cc2b7a7240272a7 · fixed in a29f57a14c939586d84d7fd6a029bd1fd170098f; From 8f0541186e9ad1b62accc9519cc2b7a7240272a7 · fixed in a4a307d149327dad5fb25187e1b03cebd1b04de6; From 8f0541186e9ad1b62accc9519cc2b7a7240272a7 · fixed in 8e4f75e979c1d9a51b0a48ac33d0cfd5f039ec67; From 8f0541186e9ad1b62accc9519cc2b7a7240272a7 · fixed in 79decd88dd3f0d42e7fb0689b1a7853bfa302459; From 5.15.62 · fixed in 5.16; From 5.18.18 · fixed in 5.19; From 5.19.2 · fixed in 5.20

• Linux Linux

  6.0

• KernelLinux

  From 6.0.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.110; From 6.13.0 · fixed in 6.18.52; From 6.19.0 · fixed in 7.2.6

References 5