web2py before 2.14.6 does not properly check if a host is denied before verifying passwords, allowing a remote attacker to perform brute-force attacks.
https://usn.ubuntu.com/4030-1/
https://github.com/web2py/web2py/issues/1585#issuecomment-284317919
https://github.com/web2py/web2py/commit/944d8bd8f3c5cf8ae296fc03d149056c65358426