What is CVE-2021-34527?

CVE-2021-34527 is a high-severity vulnerability in Microsoft Windows 10 1507. CVSS score: 8.8/10. Published 2021-07-02.

How severe is CVE-2021-34527?

High severity. CVSS v3 base score is 8.8 out of 10.

Is CVE-2021-34527 known to be exploited?

Yes. CVE-2021-34527 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating it is being actively exploited. 367 public proof-of-concept repositories are indexed.

PrintNightmare — Microsoft Windows 10 1507 Vulnerability

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.

EPSS: 0.998 (100.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

Affected products

Microsoft Windows_10_1507
Microsoft Windows_10_1607
Microsoft Windows_10_1809
Microsoft Windows_10_20h2
Microsoft Windows_10_21h2
Microsoft Windows_10_22h2
Microsoft Windows 10 Version 1507 — versions 10.0.10240.0, 10.0.0
Microsoft Windows 10 Version 1607 — versions 10.0.14393.0, 10.0.0
Microsoft Windows 10 Version 1809 — versions 10.0.0, 10.0.17763.0
Microsoft Windows 10 Version 20h2 — versions 10.0.0

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2021-11-03. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2022-05-03.

Required action: Apply updates per vendor instructions.

Known ransomware campaign use: yes.

Public proof-of-concept exploits

References

af854a3a-2127-422b-91ae-364da2661108 (Patch, x_refsource_MISC, Mitigation, Vendor Advisory)
af854a3a-2127-422b-91ae-364da2661108 (Exploit, x_refsource_MISC, Third Party Advisory, VDB Entry)
af854a3a-2127-422b-91ae-364da2661108 (Third Party Advisory, US Government Resource)
af854a3a-2127-422b-91ae-364da2661108 (Exploit, Third Party Advisory)
af854a3a-2127-422b-91ae-364da2661108 (Exploit, Third Party Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)
secure@microsoft.com (vendor-advisory, Patch, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2021-34527?: CVE-2021-34527 is a high-severity vulnerability in Microsoft Windows 10 1507. CVSS score: 8.8/10. Published 2021-07-02.
How severe is CVE-2021-34527?: High severity. CVSS v3 base score is 8.8 out of 10.
Is CVE-2021-34527 known to be exploited?: Yes. CVE-2021-34527 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating it is being actively exploited. 367 public proof-of-concept repositories are indexed.