Exim Dictionary Attack ACL *Exploit*

If you’re still using our old exim_deny dictionary attack solution in cPanel you should stop doing so and exclusively use the one provided by cPanel in cPanel v11. An exploit vector has been found and published for our old method:http://paste2.org/p/12037However, using that exploit method would be quite tricky because the exim_deny.pl script generates that lock file when the very first email passes through the ACL after installation and from then on it wouldn’t be possible to use the above exploit. That is, someone would have to create the symlink as described in the time between you adding the ACL into exim and the first email arriving. Alternatively, if you actively and indiscriminately delete files from /tmp, then the exploit could be applied between the time of deleting the lock file and the next email passes through exim.Such a short window of opportunity makes the exploit as described extremely unlikely as the hacker would have no idea when you’re going to install the ACL or to do it in advance of installation.We’re not aware of anyone being exploited through the use of this method.Incidentally, if you’re running csf, then lfd would pick up this type of issue through LF_DIRWATCHMany thanks to Billy for bringing this to our attention.The simplest way to remove our old exim_deny method is to select the option in WHM > Exim Configuration Editor > Reset ACL Config to Defaults and then remove the exim_deny files: