usercp_register.php in phpBB 2.0.17 allows remote attackers to modify regular expressions and execute PHP code via the signature_bbcode_uid parameter, as demonstrated by injecting an "e" modifier into a preg_replace statement.
AV:N/AC:L/Au:N/C:P/I:P/A:P
This vulnerability has a 2.37% probability of being exploited in the next 30 days, ranking higher than 83% of all scored CVEs.