In TightVNC 1.3.10 there is an integer signedness error and resultant heap-based buffer overflow in InitialiseRFBConnection in rfbproto.c (for the vncviewer component). There is no check on the size given to malloc e.g. -1 is accepted. This allocates a chunk of size zero which will give a heap pointer. However one can send 0xffffffff bytes of data which can have a DoS impact or lead to remote code execution.