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 SRVMULTI response containing a SRVUSERONLINE response packet and a SRVMETAUSER response packet with long (1) nickname, (2) firstname, (3) lastname, or (4) email address fields, as exploited by the Witty worm.