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Fencer Vulns
high 8.8

CVE-2021-34527 kev+ ransomware in the critical feed json

Windows Print Spooler Remote Code Execution Vulnerability

published 2021-07-02 5 y ago modified 2026-08-10 2 mo ago also EUVD-2021-21181

cvss
8.8
version 3.1, CNA
cisa kev
Exploited
added 2021-11-03, used in ransomware
epss
99.8%
EPSS 99.8% chance of exploitation in 30 days, percentile 99.9%
public exploits
1
Metasploit

Summary

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.

Patch / fix

cisa required action Apply updates per vendor instructions.

  • Microsoft Windows 10 Version 1507 10.0.10240.18969
  • Microsoft Windows 10 Version 1607 10.0.14393.4470
  • Microsoft Windows 10 Version 1809 10.0.17763.2029
  • Microsoft Windows 10 Version 20H2 10.0.19042.1083
  • Microsoft Windows 10 Version 21H2 10.0.19044.1415
  • Microsoft Windows 10 Version 22H2 10.0.19045.2251
  • Microsoft Windows 11 version 21H2 10.0.22000.318
  • Microsoft Windows 11 version 22H2 10.0.22621.674
  • Microsoft Windows 8.1 6.3.9600.20046
  • Microsoft Windows Server 2008 R2 Service Pack 1 6.1.7601.25633
  • Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) 6.1.7601.25633
  • Microsoft Windows Server 2008 Service Pack 2 6.0.6003.21138
  • Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) 6.0.6003.21138
  • Microsoft Windows Server 2012 6.2.9200.23383
  • Microsoft Windows Server 2012 (Server Core installation) 6.2.9200.23383
  • Microsoft Windows Server 2012 R2 6.3.9600.20046
  • Microsoft Windows Server 2012 R2 (Server Core installation) 6.3.9600.20046
  • Microsoft Windows Server 2016 10.0.14393.4470
  • Microsoft Windows Server 2016 (Server Core installation) 10.0.14393.4470
  • Microsoft Windows Server 2019 10.0.17763.2029
  • Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.2029
  • Microsoft Windows Server 2022 10.0.20348.230
  • Microsoft Windows Server version 20H2 10.0.19042.1083

Timeline

  1. First public exploit (Metasploit exploit/windows/dcerpc/cve_2021_1675_printnightmare)
  2. Published
  3. Added to CISA KEV
  4. CISA patch deadline
  5. CISA SSVC: exploitation active

Known exploited

Added
5 y ago
Patch by
2022-05-03 (4 y ago)
Ransomware
Known to be used in ransomware campaigns
Required action
Apply updates per vendor instructions.
Vendor, product
Microsoft, Windows
CISA name
Microsoft Windows Print Spooler Remote Code Execution Vulnerability

Ransomware

Groups reported to have exploited it in intrusions.

  • Conti ransomware gang
  • Vice Society ransomware gang
  • Magniber ransomware gang
  • BlackBasta ransomware gang

reported by blog.talosintelligence.comcrowdstrike.comcisa.govcisa.gov

Ransomware Vulnerability Matrix by BushidoUK (github.com/BushidoUK/Ransomware-Vulnerability-Matrix), reformatted per CVE. CC BY 4.0

CISA SSVC

Exploitation
Active, exploited in the wild
Automatable
no
Technical impact
total
Assessed
2 y ago

Exploit prediction

99.79% chance of exploitation in the next 30 days, higher than 99.9% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • Metasploit exploit/windows/dcerpc/cve_2021_1675_printnightmare Print Spooler Remote DLL Injection metasploit exploit, normal rank, 2021-06-08
  • vicarius.io https://www.vicarius.io/vsociety/posts/cve-2021-34527-printnightmare-detection-script referenced PoC, tagged "exploit" by a source, unverified
  • vicarius.io https://www.vicarius.io/vsociety/posts/cve-2021-34527-printnightmare-mitigation-script referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com http://packetstormsecurity.com/files/167261/Print-Spooler-Remote-DLL-Injection.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
CNA 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 9.0 AV:N/AC:L/Au:S/C:C/I:C/A:C

Affected products

  • Microsoft Windows 10 Version 1507
  • Microsoft Windows 10 Version 1607
  • Microsoft Windows 10 Version 1809
  • Microsoft Windows 10 Version 20H2
  • Microsoft Windows 10 Version 21H2
  • Microsoft Windows 10 Version 22H2
  • Microsoft Windows 11 version 21H2
  • Microsoft Windows 11 version 22H2
  • Microsoft Windows 8.1
  • Microsoft Windows Server 2008 R2 Service Pack 1
  • Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation)
  • Microsoft Windows Server 2008 Service Pack 2
  • Microsoft Windows Server 2008 Service Pack 2 (Server Core installation)
  • Microsoft Windows Server 2012
  • Microsoft Windows Server 2012 (Server Core installation)
  • Microsoft Windows Server 2012 R2
  • Microsoft Windows Server 2012 R2 (Server Core installation)
  • Microsoft Windows Server 2016
  • Microsoft Windows Server 2016 (Server Core installation)
  • Microsoft Windows Server 2019
  • Microsoft Windows Server 2019 (Server Core installation)
  • Microsoft Windows Server 2022
  • Microsoft Windows Server version 20H2

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.