Minimal configuration

./configure  --without-mysql --with-apache=../apache_1.3.20 --without-gd --without-zlib --without-gdbm
--without-shared-apache --with-mcrypt

libmcrypt versions 2.2.7, 2.4.10, 2.4.11, 2.4.15
php versions 4.0.4pl1, 4.0.5, 4.0.6

This script leaks about 6MB per execution on my system.

<PRE>
<?
$key = "87654321";

for ($i = 500; $i--; )
    $input .= '1234567890';

require("Crypt/CBC.php");

$CBC = new Crypt_CBC($key, "DES");
$block = $CBC->encrypt($input);
$x = $CBC->decrypt($block);

if ($x != $input)
    print "$x\n";
?>
</PRE>

Modifying PEAR/Crypt/CBC.php to use mcrypt_ecb() instead of
mcrypt_generic() reduces memory leak to less than 1MB
after 1000 executions.