ruby -- multiple vulnerabilities in safe level

The official ruby site reports:

Several vulnerabilities in safe level have been discovereds:.

untrace_var is permitted at safe level 4;
$PROGRAM_NAME may be modified at safe level 4;
insecure methods may be called at safe level 1-3;
syslog operations are permitted at safe level 4;
dl doesn’t check taintness, so it could allow attackers
to call dangerous functions.