Microsoft documentation for GetEffectiveRightsFromAclW function that was used previously has this at the top of the page: > GetEffectiveRightsFromAcl is available for use in the operating > systems specified in the Requirements section. It may be altered > or unavailable in subsequent versions. Instead, use the method > demonstrated in the example below. This says to me that the function is deprecated. In addition to that, it is not able to handle ACLs that are not in "canonical" order, returning ERROR_INVALID_ACL. Such ACLs are useful to represent POSIX permissions in Windows, and are produced by Cygwin for example. This patch uses Authz API referenced by the message quoted above. The used API is available starting from Windows XP/Windows Server 2003. This API also allowe to perform access checks given access token, and so allows to use similar code all permission checks. Task-number: QTBUG-79750 Change-Id: I8b11ff3cc83cd9ed5bfb2ce9432a375a122cdbbf Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org> Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>