Microsoft ActiveSync 4.1, as used in Windows Mobile 5.0, uses weak encryption (XOR obfuscation with a fixed key) when sending the user's PIN/Password over the USB connection from the host to the device, which might make it easier for attackers to decode a PIN/Password obtained by (1) sniffing or (2) spoofing the docking process.
https://exchange.xforce.ibmcloud.com/vulnerabilities/37223
https://euvd.enisa.europa.eu/vulnerability/EUVD-2007-5436
http://www.securityfocus.com/bid/25976
http://www.securityfocus.com/archive/1/482299/100/0/threaded