This exploit targets a heap overflow vulnerability in the RegisterCom() function of the AntCore.dll library in Bigant Messenger version 2.52 and earlier. The vulnerability allows an attacker to remotely execute arbitrary code on a vulnerable system. The exploit takes advantage of this vulnerability to create a custom HTTP response that triggers the overflow and executes the attacker's code. This exploit has been tested on Windows XP SP3 with Internet Explorer 6 and 7.