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>

Workaround for Windows Print Spooler Remote Code Execution Vulnerability(CVE-2021-34527). See: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527

# disable-RegisterSpoolerRemoteRpcEndPoint
Workaround for Windows Print Spooler Remote Code Execution Vulnerability(CVE-2021-34527). See:
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527

## Update 2021-07-08: Microsoft released a patch
Microsoft already released a patch for this vulnerability, so keeping your system up to date should be enough.
However, you can still turn off this functionality if you want (maybe because you don't use it or maybe because you still don't feel safe).

## How to use it
Download an execute with admin privileges.

## What this script does
It creates a new register entry (or overrides the existing one) to disable remote connections to the print spooler.
To be more specific, it does the same as this policy change:
https://admx.help/?Category=Windows_10_2016&Policy=Microsoft.Policies.Printing.2::RegisterSpoolerRemoteRpcEndPoint

If you prefer to do it manually, you can follow the 2nd option of the "Workaround" from:
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527

If you need a step by step guide, here's one:
  1. Open the "Run" window by pressing Win + R (Win = Windows Key)
  2. Type: gpedit.msc
  3. Press enter to load the Group Policy Editor
  4. Go to "Computer Configuration" -> "Administrative Templates" -> "Printers"
  5. Double click on "Allow Print Spooler to accept client connections" to open this directive
  6. Set the policy to "Disabled".
  7. Select OK to apply the changes.
  8. Restart the computer for the "Spool" service to see and take into account the changes

## Caveats
The print server will no longer accept remote connections (it can be undone).

 [4.0K]  /data/pocs/c230ad4ac0b0cc1331dca062b1e5a3ec8ede1bb2
├── [1.4K]  disable-RegisterSpoolerRemoteRpcEndPoint.bat
├── [1.1K]  LICENSE
└── [1.6K]  README.md

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