Java 2 Micro-Edition Connected Limited Device Con- figuration (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. Second, 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. The aspects targeted by this security analysis encompass: Networking, record management system, virtual machine, multi-threading and digital right management. This work identifies security weaknesses in J2ME CLDC that may represent sources of security exploits. Moreover, the results reported in this paper are valuable for any attempt to test or harden the security of this platform.