PunBB 1.2.9, used alone or with F-ART BLOG:CMS, may trust a client's IP address as specified in the X-Forwarded-For HTTP header rather than the TCP/IP stack, which allows remote attackers to misrepresent their IP address by sending a modified header.
admin_loader.php in PunBB 1.2.1 allows remote attackers to read arbitrary files via the plugin parameter.
PunBB 1.2.10 and earlier allows remote attackers to conduct brute force guessing attacks for an account's password, which may be as short as 4 characters.