Multiple stack-based buffer overflows in the ICQ parsing routines of the ISS Protocol Analysis Module (PAM) component as used in various RealSecure Proventia and BlackICE products allow remote attackers to execute arbitrary code via a SRV_MULTI response containing a SRV_USER_ONLINE response packet and a SRV_META_USER response packet with long (1) nickname (2) firstname (3) lastname or (4) email address fields as exploited by the Witty worm.