According to these Russians, They cracked the Yahoo Captcha and are giving away how they did it here.
The implementation of yahoo CAPTCHA recognition engine is here . It consists of two projects (client and server).
First project (server) needs MATLAB 2007a Compiler Runtime (MCR) installed. It waits for a connection and receives CAPTCHA, after that it sends recognized CAPTCHA text string back to client.
Client reads jpg-files in test1 directory and sends them one by one to the server located on the same machine.
btw, I have tested it.