CVE-2021-34527 PoC — Windows Print Spooler Remote Code Execution Vulnerability

Title:Windows Print Spooler Remote Code Execution Vulnerability (CVE-2021-34527)
Description:<p>A remote code execution vulnerability exists when the Windows Print Spooler service improperly performs privileged file operations. An attacker who successfully exploited this vulnerability could run arbitrary code with SYSTEM privileges. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.</p> <p>UPDATE July 7, 2021: The security update for Windows Server 2012, Windows Server 2016 and Windows 10, Version 1607 have been released. Please see the Security Updates table for the applicable update for your system. We recommend that you install these updates immediately. If you are unable to install these updates, see the FAQ and Workaround sections in this CVE for information on how to help protect your system from this vulnerability.</p> <p>In addition to installing the updates, in order to secure your system, you must confirm that the following registry settings are set to 0 (zero) or are not defined (<strong>Note</strong>: These registry keys do not exist by default, and therefore are already at the secure setting.), also that your Group Policy setting are correct (see FAQ):</p> <ul> <li>HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Printers\PointAndPrint</li> <li>NoWarningNoElevationOnInstall = 0 (DWORD) or not defined (default setting)</li> <li>UpdatePromptSettings = 0 (DWORD) or not defined (default setting)</li> </ul> <p><strong>Having NoWarningNoElevationOnInstall set to 1 makes your system vulnerable by design.</strong></p> <p>UPDATE July 6, 2021: Microsoft has completed the investigation and has released security updates to address this vulnerability. Please see the Security Updates table for the applicable update for your system. We recommend that you install these updates immediately. If you are unable to install these updates, see the FAQ and Workaround sections in this CVE for information on how to help protect your system from this vulnerability. See also <a href="https://support.microsoft.com/topic/31b91c02-05bc-4ada-a7ea-183b129578a7">KB5005010: Restricting installation of new printer drivers after applying the July 6, 2021 updates</a>.</p> <p>Note that the security updates released on and after July 6, 2021 contain protections for CVE-2021-1675 and the additional remote code execution exploit in the Windows Print Spooler service known as “PrintNightmare”, documented in CVE-2021-34527.</p>

To fight against Windows security breach PrintNightmare! (CVE-2021-34527, CVE-2021-1675)

# PrintNightmare

Here is a project that will help to fight against Windows security breach PrintNightmare! (CVE-2021-34527)

You have to know that a patch has been released by Microsoft against this breach but is not fully functional and fight only RCE (Remote code execution) while LPE (Local privilege elevation) is still working for potential attackers.


Here are some things to do :
-

- First of all, on a client, you NEED to update your computer with last microsoft fixs even if it is not fully patching.
- Then, on a server, if installing the microsoft patch is not possible, you HAVE TO switch off then disable at startup the Windows Print Spooler Service via Services.msc or via 2 Powershell commands :
       "Stop-Service -Name Spooler -Force"  and  "Set-Service -Name Spooler -StartupType Disabled".
- Launch the script powershell or batch that will update or create 3 registry keys : 
    - RegisterSpoolerRemoteRpcEndPoint with value 2 (DWORD) at HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\Printers 
    - NoWarningNoElevationOnInstall with value 0 (DWORD) at HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\Printers\PointAndPrint 
    - UpdatePromptSettings with value 0 (DWORD) at HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\Printers\PointAndPrint
 
 Sources
 -
 I created this protocol with help of many websites tracing the breach : 
 - https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527
 - https://kb.cert.org/vuls/id/383432
 - https://wccftech.com/windows-printnightmare-patch-requires-additional-registry-settings/
 - https://www.ghacks.net/2021/07/03/workaround-for-the-windows-print-spooler-remote-code-execution-vulnerability/

 [4.0K]  /data/pocs/903def9914f35000884d89441a6bd0b4d57a10b0
├── [182K]  PrintNightmare Flowchart.png
├── [1.6K]  README.md
├── [ 786]  Script_PrintNightmare_Batch.bat
└── [2.2K]  Script_PrintNightmare_PShell.ps1

0 directories, 4 files