APR-util versions 1.6.3 (and earlier) function apr_password_validate() was not constant-time with regards to hashes or passwords comparisons, potentially leaking their content via a side channel timing attack particularly on platforms without crypt() such as Windows, BeOS, NetWare, or Android. Users are recommended to upgrade to version 1.6.4, which fixes this issue.
https://lists.apache.org/thread/2v8o3bj9pb7lfcr57bdnjg9xfkj04mg5