int mp_pack(lua_State *L) {
    int nargs = lua_gettop(L);
    int i;
    mp_buf *buf;

     if (nargs == 0)
         return luaL_argerror(L, 0, "MessagePack pack needs input.");
 
     buf = mp_buf_new(L);
     for(i = 1; i <= nargs; i++) {
         /* Copy argument i to top of stack for _encode processing;
         * the encode function pops it from the stack when complete. */
        lua_pushvalue(L, i);

        mp_encode_lua_type(L,buf,0);

        lua_pushlstring(L,(char*)buf->b,buf->len);

        /* Reuse the buffer for the next operation by
         * setting its free count to the total buffer size
         * and the current position to zero. */
        buf->free += buf->len;
        buf->len = 0;
    }
    mp_buf_free(L, buf);

    /* Concatenate all nargs buffers together */
    lua_concat(L, nargs);
    return 1;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.