CMIS defines an "object-only" ACL propagation mode which allows you to set permissions that don't inherit, but Alfresco does not support it last I checked. Furthermore, CMIS does not define an ACL inheritance model and thus does not provide a simple "disable inheritance" operation. There was a <a href="https://lists.oasis-open.org/archives/cmis-comment/201304/msg00005.html">similar topic on the mailing list</a> last year explaining the reasons behind that - I believe that this hasn't changed.
In short: No, unfortunately there is no (pure) CMIS way to disable inheritance while creating folders or documents. You could hack around it using aspects / properties and behaviours / rules as a kind of "cheat".
