Using mcrypt 2.6.8, libmcrypt 2.5.8-18 (libmcrypt.so.4.4.8) from the Fedora 24 repositories on an x86_64 box, running mcrypt under valgrind gives a "Use of uninitialised value of size 8" message. "file" says of the encrypted file:
mcrypt 2.5 encrypted data, algorithm: rijndael-128, keysize: 32 bytes, mode: cbc,
This happens when encrypting a file containing the text "adsasdasd" (minus the quotes) with the passphrase "12345678" (minus the quotes).