CVE-2021-34527: Windows Print Spooler Remote Code Execution Vulnerability
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):
HKEYLOCALMACHINE\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.
Other sources
Microsoft Windows Print Spooler contains an unspecified vulnerability due to the Windows Print Spooler service improperly performing privileged file operations. Successful exploitation allows an attacker to perform remote code execution with SYSTEM privileges. The vulnerability is also known under the moniker of PrintNightmare.
— CISA
Windows Print Spooler Remote Code Execution Vulnerability
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
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Fixed in 10.0.19045.2251Patch KB5019959 - Upgrade
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Fixed in 10.0.22621.674Patch KB5018427 - Upgrade
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Fixed in 10.0.19044.1415Patch KB5008212 - Upgrade
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Fixed in 10.0.20348.230Patch KB5005575 - Upgrade
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Fixed in 10.0.22000.318Patch KB5007215 - Upgrade
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Fixed in 6.3.9600.20046Patch KB5004958 - Upgrade
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Fixed in 6.2.9200.23383Patch KB5004960 - Upgrade
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Fixed in 6.0.6003.21138Patch KB5004959 - Upgrade
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Fixed in 6.1.7601.25633Patch KB5004951 - Upgrade
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Fixed in 6.3.9600.20046Patch KB5004954 - Upgrade
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Fixed in 10.0.14393.4470Patch KB5004948 - Upgrade
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Fixed in 10.0.10240.18969Patch KB5004950 - Upgrade
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Fixed in 10.0.19042.1083Patch KB5004945 - Upgrade
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Fixed in 10.0.17763.2029Patch KB5004947 - Upgrade
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Patch KB5005010 - Configuration
In HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Printers\PointAndPrint, ensure NoWarningNoElevationOnInstall is set to 0 (DWORD) or is not defined (default secure state).
Windows Print Spooler PointAndPrint (Group Policy registry keys) NoWarningNoElevationOnInstall = 0 (DWORD) or not defined - Configuration
In HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Printers\PointAndPrint, ensure UpdatePromptSettings is set to 0 (DWORD) or is not defined (default secure state).
Windows Print Spooler PointAndPrint (Group Policy registry keys) UpdatePromptSettings = 0 (DWORD) or not defined
Event History
Peer vulnerabilities
Found alongside the following vulnerabilities.
Frequently Asked Questions
What is the severity of CVE-2021-34527?
CVE-2021-34527 is rated as critical due to its potential for remote code execution with SYSTEM privileges.
How do I fix CVE-2021-34527?
To fix CVE-2021-34527, apply the latest security updates provided by Microsoft for the affected Windows versions.
Which versions of Windows are affected by CVE-2021-34527?
CVE-2021-34527 affects several versions including Windows 10, Windows Server 2019, Windows Server 2022, and Windows 11.
What type of attack does CVE-2021-34527 enable?
CVE-2021-34527 enables an attacker to execute arbitrary code on the target machine by exploiting the Windows Print Spooler service.
Is there a workaround for CVE-2021-34527?
Yes, disabling the Print Spooler service on systems where it is not needed can serve as a temporary workaround for CVE-2021-34527.