========================================
  INetCop Security Advisory #2006-0x82-029
  ========================================


* Title: zeroboard IP session bypass XSS vulnerability


0x01. Description


Zeroboard is a popular web notice board used in Korea.

INetCop Security found XSS vulnerability in the latest zeroboard version 4.1 pl 7 (2005. 4. 4).
Basically, zeroboard uses the following algorithm so that session may not be abused
by the attack related with cookie. (e.g: cookie spoofing, sniffing)

After login, is part that handle session: --

bbs/login_check.php:
...
    24  // ȸ¿ø·Î±×ÀÎÀÌ ¼º°øÇÏ¿´À» °æ¿ì ¼¼¼ÇÀ» »ý¼ºÇÏ°í ÆäÀÌÁö¸¦ À̵¿ÇÔ
    25          if($member_data[no]) {
    26
    27                  if($auto_login) {
    28                          makeZBSessionID($member_data[no]);
    29                  }
    30
    31                  // 4.0x ¿ë ¼¼¼Ç ó¸®
    32                  $zb_logged_no = $member_data[no];
    33                  $zb_logged_time = time();
    34                  $zb_logged_ip = $REMOTE_ADDR; <--- Recording IP address
    35                  $zb_last_connect_check = '0';
    36
    37                  session_register("zb_logged_no");
    38                  session_register("zb_logged_time");
    39                  session_register("zb_logged_ip");
    40                  session_register("zb_last_connect_check");
    41
--

If IP address is different from present session user's, connection terminates: --

bbs/lib.php:

    94                  // ¼¼¼Ç °ªÀ» üũÇÏ¿© ·Î±×ÀÎÀ» ó¸®
    95                  } elseif($HTTP_SESSION_VARS["zb_logged_no"]) {
    96
    97                          // ·Î±×ÀÎ ½Ã°£ÀÌ ÁöÁ¤µÈ ½Ã°£À» ³Ñ¾ú°Å³ª ·Î±×ÀÎ
¾ÆÀÌÇÇ°¡ ÇöÀç »ç¿ëÀÚÀÇ ¾ÆÀÌÇÇ¿Í ´Ù¸¦ °æ¿ì ·Î±×¾Æ¿ô ½ÃÅ´
    98                          if(time()-$HTTP_SESSION_VARS["zb_logged_time"]>
$_zbDefaultSetup["login_time"]||$HTTP_SESSION_VARS["zb_logged_ip"]!=$REMOTE_ADDR)
 {
    99
   100                                  $zb_logged_no=""; // session initialization
   101                                  $zb_logged_time="";
   102                                  $zb_logged_ip="";
   103                                  session_register("zb_logged_no");
   104                                  session_register("zb_logged_ip");
   105                                  session_register("zb_logged_time");
   106                                  session_destroy();
   107
   108                          // À¯È¿ÇÒ °æ¿ì ·Î±×ÀÎ ½Ã°£À» ´Ù½Ã ¼³Á¤
   109                          } else {
--


This seems to be intercepting cookie hacking.
But, if we take advantage of IP session disablement technique, session bypassing may be possible.
Detailed explanation about the way to exploit this vulnerability is found at the following 

reference.

URL: http://x82.inetcop.org/h0me/papers/iframe_tag_exploit.txt (Korean)

As a result, hacker through administrator's web browser exploit code workably become.


--


0x02. Vulnerable Packages


Vendor site: http://www.nzeo.com/

Low versions including Zeroboard 4.1 pl 7 (2005. 4. 4) version.
-zb41pl7.tar.Z 

Disclosure Timeline:
2003-04.??: Vulnerabilities found.
2006-02.17: 1st vendor contact. (didn't respond)
2006-02.22: 2nd vendor contact. (didn't respond)
2006-02.25: Vendor responded, patch released.
2006-03.12: Public disclosure.


0x03. Exploit


We have 2 `Proof-of-Concept' exploit about this vulnerability.

This XSS vulnerability happens in memo box title and user email, homepage information input.
When administrator logins and checks a user information page, attack code can be achieved,
and there is another way, which injects an attack code in memo title.
After exploit, an attacker can inject PHP code through an administrator web page function.
Through this PHP code injection, the attacker(normal user) can change the password of 

administrator, 
and take administrator's privilege

To prevent the abuse of this vulnerabilty, INetCop Security will not publish POC code.


0x04. Patch


INetCop Security released temporary patch:
INetCop Security Patch URL: http://inetcop.net/upfiles/Zeroboard-4.1_pl7_patch.tgz

And vendor's patch after INetCop Security advisory:
Vendor Patch URL: http://www.nzeo.com/bbs/zboard.php?id=cgi_bugreport2&no=5406

--
Thank you.

P.S: I give thanks to Securityproof that suffer translation.
Korean Advisory URL: http://www.inetcop.org/upfiles/33INCSA.2006-0x82-029-zeroboard.pdf


--
By "dong-houn yoU" (Xpl017Elz), in INetCop(c) Security.

MSN & E-mail: szoahc(at)hotmail(dot)com,
              xploit(at)hackermail(dot)com

INetCop Security Home: http://www.inetcop.org
             My World: http://x82.inetcop.org

GPG public key: http://x82.inetcop.org/h0me/pr0file/x82.k3y
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