Vocera Communications wireless handsets, when using Protected Extensible Authentication Protocol (PEAP), do not validate server certificates, which allows remote wireless access points to steal hashed passwords and conduct man-in-the-middle (MITM) attacks.
http://www.vocera.com/downloads/InfrastructureGuide.pdf
http://www.securityfocus.com/bid/27935
http://seclists.org/fulldisclosure/2008/Feb/0402.html