CVE-2026-90153

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

Affected Software

VendorProductVersion RangeStatus
LinuxLinux8f0541186e9ad1b62accc9519cc2b7a7240272a7 < a2051ffe452afad52f580b85a3fd8851933b1e7caffected
LinuxLinux8f0541186e9ad1b62accc9519cc2b7a7240272a7 < a29f57a14c939586d84d7fd6a029bd1fd170098faffected
LinuxLinux8f0541186e9ad1b62accc9519cc2b7a7240272a7 < a4a307d149327dad5fb25187e1b03cebd1b04de6affected
LinuxLinux8f0541186e9ad1b62accc9519cc2b7a7240272a7 < 8e4f75e979c1d9a51b0a48ac33d0cfd5f039ec67affected
LinuxLinux8f0541186e9ad1b62accc9519cc2b7a7240272a7 < 79decd88dd3f0d42e7fb0689b1a7853bfa302459affected
LinuxLinuxcb69d4d6f709f87c94afa28ae64c501576692171affected
LinuxLinux6e8f4abf584253cbaa596ea4ad13110cf61cd4c9affected
LinuxLinux8e33102309bd6839b2e2e158f93a7b378cb4655daffected
LinuxLinux5.15.62 < 5.16affected
LinuxLinux5.18.18 < 5.19affected
LinuxLinux5.19.2 < 5.20affected
LinuxLinux6.0affected
LinuxLinux0 < 6.0unaffected
LinuxLinux6.6.157 <= 6.6.*unaffected
LinuxLinux6.12.110 <= 6.12.*unaffected
LinuxLinux6.18.52 <= 6.18.*unaffected
LinuxLinux7.2.6 <= 7.2.*unaffected
LinuxLinux7.3-rc1 <= *unaffected

Weaknesses

References