Java 2 Micro-Edition Connected Limited Device Configuration (J2ME CLDC) is the platform of choice when it comes to running mobile applications on resourceconstrained devices (cell phones, set-top boxes, etc.). The large deployment of this platform makes it a target for security attacks. The intent of this paper is twofold: First, we study the security architecture of J2ME CLDC, then we provide a vulnerability analysis of this Java platform. The analyzed components are: Virtual machine, CLDC API and MIDP (Mobile Information Device Profile) API. The analysis covers the specifications, the reference implementation (RI) as well as several other widely-deployed implementations of this platform.