<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>
Conclusion & alert: CVE-2021-34527 is rated Critical Active Threat (100/100): CVSS High severity, with high exploitation likelihood (EPSS 99.76%, 100th percentile). Core evidence: CISA KEV confirms active exploitation (added 2021-11-03) affecting Microsoft / Windows. Unauthenticated remote administrative access may be possible. EPSS rose +5.56% over the last day, indicating growing attacker interest. Mandatory action: The CISA remediation deadline has passed—treat as an emergency patch priority.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
: Microsoft Windows Print Spooler Remote Code Execution Vulnerability · CISA KEV detail
: 2021-11-03
: 2022-05-03
: Apply updates per vendor instructions.
| EDB-ID | Source | Kind | Published | Link |
|---|---|---|---|---|
| — | nvd_ref | exploit_tag | Exploit-DB ↗ | |
| — | nvd_ref | exploit_tag | Exploit-DB ↗ | |
| — | nvd_ref | exploit_tag | Exploit-DB ↗ |
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-06-15 | 94.20% | 99.76% | +5.56% |
| 2 | 2026-03-15 | 94.27% | 94.20% | -0.07% |
| 3 | 2025-12-28 | — | 94.27% | — |
Full EPSS history (34 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 8.8 | 3.1 | HIGH |
|
2.8 | 5.9 | [email protected] |
| 8.8 | 3.1 | HIGH |
|
2.8 | 5.9 | [email protected] |
| 9.0 | 2.0 | HIGH |
|
8.0 | 10.0 | [email protected] |
| Vendor | Product | Version | Raw CPE |
|---|---|---|---|
| microsoft | windows_10_1507 | < 10.0.10240.18969 | cpe:2.3:o:microsoft:windows_10_1507:*:*:*:*:*:*:*:* |
| microsoft | windows_10_1607 | < 10.0.14393.4470 | cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:*:* |
| microsoft | windows_10_1809 | < 10.0.17763.2029 | cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:*:* |
| microsoft | windows_10_20h2 | < 10.0.19042.1083 | cpe:2.3:o:microsoft:windows_10_20h2:*:*:*:*:*:*:*:* |
| microsoft | windows_10_21h2 | < 10.0.19044.1415 | cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:*:* |
| microsoft | windows_10_22h2 | < 10.0.19045.2251 | cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:*:* |
| microsoft | windows_11_21h2 | < 10.0.22000.318 | cpe:2.3:o:microsoft:windows_11_21h2:*:*:*:*:*:*:*:* |
| microsoft | windows_11_22h2 | < 10.0.22621.674 | cpe:2.3:o:microsoft:windows_11_22h2:*:*:*:*:*:*:*:* |
| microsoft | windows_7 | — | cpe:2.3:o:microsoft:windows_7:-:sp1:*:*:*:*:*:* |
| microsoft | windows_8.1 | — | cpe:2.3:o:microsoft:windows_8.1:-:*:*:*:*:*:*:* |
| microsoft | windows_rt_8.1 | — | cpe:2.3:o:microsoft:windows_rt_8.1:-:*:*:*:*:*:*:* |
| microsoft | windows_server_2008 | — | cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:*:* |
| microsoft | windows_server_2008 | r2 | cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:* |
| microsoft | windows_server_2012 | — | cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:* |
| microsoft | windows_server_2012 | r2 | cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:* |
| microsoft | windows_server_2016 | < 10.0.14393.4470 | cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:* |
| microsoft | windows_server_2019 | < 10.0.17763.2029 | cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:* |
| microsoft | windows_server_2022 | < 10.0.20348.230 | cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:* |
| microsoft | windows_server_20h2 | < 10.0.19042.1083 | cpe:2.3:o:microsoft:windows_server_20h2:*:*:*:*:*:*:*:* |
| URL | Tags |
|---|---|
| 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 |