CVE-2021-34527
HighExploitedPublic exploitA remote code execution vulnerability exists when the Windows Print Spooler service improperly performs privileged file operations.
Published Jul 7, 2021 · Updated Aug 10, 2026 · Also known as Print Nightmare, PrintNightmare
Key Facts
Patch immediately- CVE-2021-34527 is a high-severity vulnerability (CVSS 8.8 v3.1) affecting Windows 10 1507 (Microsoft), Windows 10 1607 (Microsoft), Windows 10 1809 (Microsoft) and 17 more products.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jul 2, 2021 and is known to be used in ransomware campaigns. Public exploit code is available.
- EPSS estimates a 100% probability of exploitation in the next 30 days.
- Fixed versions are available, including Windows 10 1507 10.0.10240.18969, Windows 10 1607 10.0.14393.4470, Windows 10 1809 10.0.17763.2029.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
8.8
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
100%
Higher than 99.9% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings, used by ransomware
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2021-34527 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Nov 3, 2021 | May 3, 2022 | Known |
| Industry KEV feed | Jul 2, 2021 | May 3, 2022 | Known |
| CIRCL KEV | Nov 3, 2021 | May 3, 2022 | Known |
| ENISA EUVD | Nov 3, 2021 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
48 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Windows 10 1507Microsoft | 10.0.10240.18969 | 10.0.10240.18969 |
| Windows 10 1607Microsoft | 10.0.14393.4470 | 10.0.14393.4470 |
| Windows 10 1809Microsoft | 10.0.17763.2029 | 10.0.17763.2029 |
| windows 10 20H2Microsoft | 10.0.19042.1083 | 10.0.19042.1083 |
| windows 10 21H2Microsoft | 10.0.19044.1415 | 10.0.19044.1415 |
Patched Releases
Windows 10 1507
10.0.10240.18969
Windows 10 1607
10.0.14393.4470
Windows 10 1809
10.0.17763.2029
windows 10 20H2
10.0.19042.1083
windows 10 21H2
10.0.19044.1415
windows 10 22H2
10.0.19045.2251
windows 11 21H2
10.0.22000.318
windows 11 22H2
10.0.22621.674
Windows Rt 8.1
6.3.9600.20046
windows server 2008 R2
6.1.7601.25633
Windows Server 2008 Sp2
6.0.6003.21138
Windows Server 2012
6.2.9200.23383
windows server 2012 R2
6.3.9600.20046
Windows Server 2016
10.0.14393.4470
Windows Server 2019
10.0.17763.2029
Windows Server 2022
10.0.20348.230
windows server 20H2
10.0.19042.1083
Timeline
Added to Industry KEV feed
Jul 2, 2021
Publicly disclosed
Jul 7, 2021
Added to CISA KEV
Nov 3, 2021
Added to CIRCL KEV
Nov 3, 2021
Added to ENISA EUVD
Nov 3, 2021
Last updated
Aug 10, 2026
References
- advisoryhttps://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-1675
- advisoryhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527
- advisoryhttps://us-cert.cisa.gov/ncas/current-activity/2021/06/30/printnightmare-critical-windows-print-spooler-vulnerability
- advisoryhttps://www.bankinfosecurity.co.uk/governance-risk-management-c-93
- advisoryhttps://www.bankinfosecurity.co.uk/microsoft-issues-new-mitigation-advice-on-printnightmare-a-16989
FAQ
Common Questions.
A remote code execution vulnerability exists when the Windows Print Spooler service improperly performs privileged file operations.
Affected: Windows 10 1507 (Microsoft) versions 10.0.10240.18969; Windows 10 1607 (Microsoft) versions 10.0.14393.4470; Windows 10 1809 (Microsoft) versions 10.0.17763.2029, among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jul 2, 2021 and is known to be used in ransomware campaigns.
Yes. It was added on Nov 3, 2021 with a federal remediation due date of May 3, 2022.
Public exploit code is available.
Fixed versions are available, including Windows 10 1507 10.0.10240.18969, Windows 10 1607 10.0.14393.4470, Windows 10 1809 10.0.17763.2029.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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