==================================================================== == Subject: Authenticated users can change other users' password == == CVE ID#: CVE-2018-1057 == == Versions: All versions of Samba from 4.0.0 onwards. == == Summary: On a Samba 4 AD DC any authenticated user can change == other users' passwords over LDAP, including the == passwords of administrative users and service == accounts. == ==================================================================== =========== Description =========== On a Samba 4 AD DC the LDAP server in all versions of Samba from 4.0.0 onwards incorrectly validates permissions to modify passwords over LDAP allowing authenticated users to change any other users' passwords, including administrative users and privileged service accounts (eg Domain Controllers). The LDAP server incorrectly validates certain LDAP password modifications against the "Change Password" privilege, but then performs a password reset operation. The change password right in AD is an extended object access right with the GUID ab721a53-1e2f-11d0-9819-00aa0040529b. By default user objects grant the change password right to the authenticated user's own user object (self) and to everyone (world). Computer objects grant the change password right to everyone. The corresponding ACEs expressed in SDDL are self: (OA;;CR;ab721a53-1e2f-11d0-9819-00aa0040529b;;PS) world: (OA;;CR;ab721a53-1e2f-11d0-9819-00aa0040529b;;WD) The components of these ACEs are OA: object access allowed CR: extended rights PS: trustee: self WD: trustee: world/everyone The problematic ACE is the one for world/everyone. The Windows GUI shows this as "Change password" right granted to "Everyone". ========== Workaround ========== Possible workarounds are described at a dedicated page in the Samba wiki: https://wiki.samba.org/index.php/CVE-2018-1057 ================== Patch Availability ================== A patch addressing this defect has been posted to https://www.samba.org/samba/security/ Additionally, Samba 4.7.6, 4.6.14 and 4.5.16 have been issued as security releases to correct the defect. Patches against older Samba versions may be available at https://samba.org/samba/patches/. Samba vendors and administrators running affected versions are advised to upgrade or apply the patch as soon as possible. ======= Credits ======= This problem was found by BjAPrn Baumbach from SerNet. Ralph BAPhme and Stefan Metzmacher from SerNet and the Samba Team provided the fix.