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

CISA Known Exploited Vulnerabilities

Name

Microsoft Windows Print Spooler Remote Code Execution Vulnerability

Vendor

Microsoft

Product

Windows

Added to the catalog

2021-11-03

Due date for US federal agencies

2022-05-03

Weaknesses

CWE-269

Catalog version

2026.10.30

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.

Required action (CISA)

Apply updates per vendor instructions.

Ransomware use: CISA marks this vulnerability as known to be used in ransomware campaigns. CISA does not say which group used it.

Links in CISA's notes

• https://www.cisa.gov/news-events/directives/ed-21-04-mitigate-windows-print-spooler-service-vulnerability)
• https://nvd.nist.gov/vuln/detail/CVE-2021-34527

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2021-07-02T22:15:08.757

Last modified

2026-08-10T20:15:22.807

Weaknesses

NVD-CWE-noinfo

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.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527 (Patch, Vendor Advisory)
• http://packetstormsecurity.com/files/167261/Print-Spooler-Remote-DLL-Injection.html (Exploit, Third Party Advisory, VDB Entry)
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34527 (Mitigation, Patch, Vendor Advisory)
• https://www.kb.cert.org/vuls/id/383432 (Third Party Advisory, US Government Resource)
• https://www.vicarius.io/vsociety/posts/cve-2021-34527-printnightmare-detection-script (Exploit, Third Party Advisory)
• https://www.vicarius.io/vsociety/posts/cve-2021-34527-printnightmare-mitigation-script (Exploit, Third Party Advisory)
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34527 (US Government Resource)

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:41:51.476Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2021-34527

CVE record

Title (CNA)

Windows Print Spooler Remote Code Execution Vulnerability

Assigner

microsoft

State

PUBLISHED

Published

2021-07-02T21:25:11.000Z

Updated

2026-08-10T15:12:05.065Z

Problem types

Remote Code Execution

References

• Windows Print Spooler Remote Code Execution Vulnerability

Read on 2026-11-03T01:08:15.167Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2021/34xxx/CVE-2021-34527.json

Detection rules (SigmaHQ)

SigmaHQ rules whose own tags name this CVE. Each rule page shows the rule as its author published it.

• Windows Spooler Service Suspicious Binary Load (status test, level informational)
• Antivirus PrinterNightmare CVE-2021-34527 Exploit Detection (status stable, level critical)
• Possible PrintNightmare Print Driver Install - CVE-2021-1675 (status stable, level medium)
• CVE-2021-1675 Print Spooler Exploitation IPC Access (status test, level critical)
• PrinterNightmare Mimikatz Driver Name (status test, level critical)