CVE-2021-34527: Windows Print Spooler Remote Code Execution Vulnerability

Overview

Severity
High (CVSS 8.8)
CVSS Vector
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
Category
Remote Code Execution
Exploit Status
Actively Exploited
Exploitation Likelihood
Detected
Publicly Disclosed
Yes
Patch Tuesday
2021-Jul
Released
2021-07-01
Last Updated
2023-06-13
EPSS Score
94.20% (percentile: 99.9%)
CISA KEV
Listed — due 2022-05-03

Description

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. 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. 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 (Note: 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): HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Printers\PointAndPrint NoWarningNoElevationOnInstall = 0 (DWORD) or not defined (default setting) UpdatePromptSettings = 0 (DWORD) or not defined (default setting) Having NoWarningNoElevationOnInstall set to 1 makes your system vulnerable by design. 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 KB5005010: Restricting installation of new printer drivers after applying the July 6, 2021 updates. 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.

FAQ

If I have not yet installed the security update released Out-of-Band on July 6 and 7, 2021, then do I need to install both the Out-of-Band security update released on July 6 and 7, 2021, and the monthly security updates released on July 13, 2021 to be protected from PrintNightmare? All monthly security updates are cumulative, including the monthly security updates released on July 13, 2021. The July 13, 2021 cumulative security updates contain all previous security fixes - including the security fix for the print spooler vulnerability (CVE-2021-34527). Customers who have not previously deployed the OOB fix released on July 6 and 7, 2021, can skip deploying the OOB update and deploy the July cumulative security updates released on July 13, 2021, to be protected. Is this the vulnerability that has been referred to publicly as PrintNightmare? Yes, Microsoft has assigned CVE-2021-34527 to this vulnerability. Is this vulnerability related to CVE-2021-1675? This vulnerability is similar but distinct from the vulnerability that is assigned CVE-2021-1675. The attack vector is different as well. CVE-2021-1675 was addressed by the security update released on June 8, 2021. Did the June 2021 update introduce this vulnerability? No, the vulnerability existed before the June 8, 2021 security update. All versions of Windows are listed in the Security Updates table. Are all versions vulnerable? All versions of Windows are vulnerable. As of July 7, 2021, Microsoft has released security updates for this vulnerability for all supported versions of Windows listed in the security updates table in this CVE. What vulnerabilities do the security updates released on and after July 6, 2021 address? The security updates released on and after July 6, 2021 contain protections for a remote code execution exploit in the Windows Print Spooler service known as “PrintNightmare”, documented in CVE-2021-34527, as well as for CVE-2021-1675. Are Domain Controllers known to be affected by the vulnerabil

Known Exploits (10)

  • Microsoft Windows Print Spooler Remote Code Execution Vulnerability — added 2024-02-12T20:54:51Z
  • Microsoft Windows Print Spooler Remote Code Execution Vulnerability — added 2023-09-08T12:59:15Z
  • Microsoft Windows Print Spooler Remote Code Execution Vulnerability — added 2022-09-05T23:48:44Z
  • Microsoft Windows Print Spooler Remote Code Execution Vulnerability — added 2022-08-23T20:20:45Z
  • Microsoft Windows Print Spooler Remote Code Execution Vulnerability — added 2022-06-24T13:25:25Z
  • Microsoft Windows Print Spooler Remote Code Execution Vulnerability — added 2021-09-26T13:53:10Z
  • Microsoft Windows Print Spooler Remote Code Execution Vulnerability — added 2021-07-09T08:27:36Z
  • Microsoft Windows Print Spooler Remote Code Execution Vulnerability — added 2021-07-03T15:15:12Z
  • Microsoft Windows Print Spooler Remote Code Execution Vulnerability — added 2021-07-02T12:10:49Z
  • Microsoft Windows Print Spooler Remote Code Execution Vulnerability — added 2021-06-29T17:24:14Z

Detection & Weaponization (2 sources)

Maturity: Exploit

  • Metasploit modules: Print Spooler Remote DLL Injection
  • GitHub PoC: 25 repositories

Affected Products (38)

Windows

  • Windows 10 Version 1809 for 32-bit Systems
  • Windows 10 Version 1809 for x64-based Systems
  • Windows 10 Version 1809 for ARM64-based Systems
  • Windows Server 2019
  • Windows Server 2019 (Server Core installation)
  • Windows Server 2022
  • Windows Server 2022 (Server Core installation)
  • Windows 10 Version 20H2 for x64-based Systems
  • Windows 10 Version 20H2 for 32-bit Systems
  • Windows 10 Version 20H2 for ARM64-based Systems
  • Windows Server, version 20H2 (Server Core Installation)
  • Windows 11 version 21H2 for x64-based Systems
  • Windows 11 version 21H2 for ARM64-based Systems
  • Windows 10 Version 21H2 for 32-bit Systems
  • Windows 10 Version 21H2 for ARM64-based Systems
  • Windows 10 Version 21H2 for x64-based Systems
  • Windows 11 Version 22H2 for ARM64-based Systems
  • Windows 11 Version 22H2 for x64-based Systems
  • Windows 10 Version 22H2 for x64-based Systems
  • Windows 10 Version 22H2 for ARM64-based Systems
  • Windows 10 Version 22H2 for 32-bit Systems
  • Windows 10 for 32-bit Systems
  • Windows 10 for x64-based Systems
  • Windows 10 Version 1607 for 32-bit Systems
  • Windows 10 Version 1607 for x64-based Systems
  • Windows Server 2016
  • Windows Server 2016 (Server Core installation)
  • Windows RT 8.1
  • Windows Server 2012
  • Windows Server 2012 (Server Core installation)
  • Windows Server 2012 R2
  • Windows Server 2012 R2 (Server Core installation)

ESU

  • Windows Server 2008 for 32-bit Systems Service Pack 2
  • Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation)
  • Windows Server 2008 for x64-based Systems Service Pack 2
  • Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation)
  • Windows Server 2008 R2 for x64-based Systems Service Pack 1
  • Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation)

Security Updates (17)

Acknowledgments

Zhiniang Peng (<a href="https://twitter.com/edwardzpeng/">@edwardzpeng</a>) and Xuefeng Li (<a href="https://twitter.com/lxf02942370/">@lxf02942370</a>), Sergii Bezus with <a href="https://10guards.com">10Guards</a>

Revision History

  • 2021-07-01: Information published.
  • 2021-07-02: The information in the workaround section was updated. This an informational change only.
  • 2021-07-02: CVE revised to update the FAQ, add a mitigation, and add the CVSS score. These are informational changes only.
  • 2021-07-02: Updated FAQ information. This is an informational change only.
  • 2021-07-03: Updated FAQ information. This is an informational change only.
  • 2021-07-06: CVE updated to announce that Microsoft is releasing an update for several versions of Window to address this vulnerability. Updates are not yet available for Windows 10 version 1607, Windows Server 2016, or Windows Server 2012. Security updates for these versions of Windows will be released soon. Other information has been updated as well. This information will be updated when more information or updates are available.
  • 2021-07-07: CVE updated to announce that Microsoft is releasing an update for Windows 10 version 1607, Windows Server 2016, and Windows Server 2012. Other information has been updated as well.
  • 2021-07-08: Added information to the executive summary and the FAQ sections. This is an informational change only.
  • 2021-07-15: Added FAQ information. This is an informational change only.
  • 2021-07-16: Added an acknowledgement. This is an informational change only.
  • 2023-06-13: In the Security Updates table, added all supported editions of Windows 10 version 21H2, Windows 11 version 21H2, Windows 11 version 22H2, and Windows Server 2022 as they are affected by this vulnerability. Customers running any of these versions of Windows should install listed updates or newer to be protected from this vulnerability. After these updates are installed, please follow the advice included in the documentation on this CVE.  With this revision, products that are no longer in support have been removed.