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ExploitedIn CISA KEVFix available

CVE-2021-34527

PrintNightmare

Exploitation confirmed. First attested on 2021-11-03 by CISA-ADP, CISA KEV, GCVE · kevintel.

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2021-07-0222:15CVE publishedNVD
  2. 2021-11-03Added to the CISA KEV catalogCISA KEV
  3. 2021-11-03Listed as exploited by GCVEGCVE
  4. 2021-11-03Exploitation first reportedCISA KEV
  5. 2024-01-2416:04SSVC exploitation set to activeCISA-ADP

Observed activity

isMalicious corpus · updated 2026-11-04 09:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-34527?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-34527?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Microsoft windows server 2008
BranchAffectedFixed in
—all versionsno fix published
—= r2no fix published
Microsoft windows server 2012
BranchAffectedFixed in
—all versionsno fix published
—= r2no fix published
Microsoft windows 10 1507
BranchAffectedFixed in
10.0< 10.0.10240.1896910.0.10240.18969

12 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA24 products

As microsoft, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • Microsoft Windows 10 Version 1507

    platforms: 32-bit Systems, x64-based Systems

    Affected
    • ≥ 10.0.10240.0, < 10.0.10240.18969fixed in 10.0.10240.18969custom
  • Microsoft Windows 10 Version 1607

    platforms: 32-bit Systems, x64-based Systems

    Affected
    • ≥ 10.0.14393.0, < 10.0.14393.4470fixed in 10.0.14393.4470custom
  • Microsoft Windows 10 Version 1809

    platforms: 32-bit Systems, x64-based Systems

    Affected
    • ≥ 10.0.17763.0, < 10.0.17763.2029fixed in 10.0.17763.2029custom
  • Microsoft Windows 10 Version 1809

    platforms: ARM64-based Systems

    Affected
    • ≥ 10.0.0, < 10.0.17763.2029fixed in 10.0.17763.2029custom
  • Microsoft Windows 10 Version 20H2

    platforms: 32-bit Systems, ARM64-based Systems

    Affected
    • ≥ 10.0.0, < 10.0.19042.1083fixed in 10.0.19042.1083custom
  • Microsoft Windows 10 Version 21H2

    platforms: 32-bit Systems, ARM64-based Systems, x64-based Systems

    Affected
    • ≥ 10.0.19044.0, < 10.0.19044.1415fixed in 10.0.19044.1415custom

18 more products in the CVE record.

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-08-10

Fix

  1. CISA’s required action: Apply updates per vendor instructions.due 2022-05-03

Advisories and patches

Detection

read 2026-11-03 22:42 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
20 repositories, unverifiedDenizSe/CVE-2021-34527JohnHammond/CVE-2021-34527twi1ight00/PrintNightmarenemo-wq/PrintNightmare-CVE-2021-34527rdboboia/disable-RegisterSpoolerRemoteRpcEndPoint
PoC-in-GitHub
Metasploit modules
1 moduleexploit/windows/dcerpc/cve_2021_1675_printnightmarerank: normalModule metadata: Metasploit Framework, © Rapid7, Inc., BSD-3-Clause.
Metasploit Framework

CISA Known Exploited Vulnerability

Date Added
2021-11-03
Patch Due Date
2022-05-03
Ransomware Use
Known
Required Action
Apply updates per vendor instructions.

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published
2021-07-02
Last Modified
2026-08-10
NVD status
Analyzed
GitHub Advisory
GHSA-75f9-mm5v-2rgm

Frequently asked questions

What is CVE-2021-34527?

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.

Is CVE-2021-34527 actively exploited?

Yes. CVE-2021-34527 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 2022-05-03.

What is the CVSS score for CVE-2021-34527?

CVE-2021-34527 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

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