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NVD / CVE Program· CNA microsoft

CVE-2021-34527: Windows Print Spooler Remote Code Execution Vulnerability

Noroxi assessment

Priority: Now (action score 95/100)

  • CISA has confirmed exploitation in the wild (Nov 3, 2021); it is known to be used in ransomware campaigns. Remediation deadline for US federal agencies: May 3, 2022.
  • A ready-made attack module is public (Metasploit); exploiting it takes no special expertise.
  • Probability of exploitation in the next 30 days: 99.7% (FIRST EPSS); higher than 99.9% of all records.
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • According to the record, no fixed version is available yet.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Patch today or shut off access. Until a fix is released, restrict access to the affected component and follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · CISA KEV · FIRST EPSS

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.

HighCVSS 8.8 · v3.1KEVWeaponized No fix recorded
Published
Jul 2, 2021
Updated
Aug 10, 2026
EPSS
99.7% · 99th percentile
CWE
—

Report tools

JSON

Action score

95

Now

Patch today or shut off access.

CVSS
35 / 40 · 8.8 / 10
CISA KEV
30 / 30 · Listed
EPSS
30 / 30 · 99.7%

CISA SSVC decision

Exploitation
active
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · microsoft
8.8
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on Nov 3, 2021. That signals real attacks, not theory.

Remediation deadline for US federal agencies: May 3, 2022.

Known to be used in ransomware campaigns.

Get told when this record changes

  • In CISA KEV: exploitation in the wild confirmed
  • Weaponized exploit exists
  • No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-34527

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
microsoftwindows 10 1507
microsoftwindows 10 1607
microsoftwindows 10 1809
microsoftwindows 10 20h2
microsoftwindows 10 21h2
microsoftwindows 10 22h2
microsoftwindows 11 21h2
microsoftwindows 11 22h2
microsoftwindows rt 8.1
microsoftwindows server 2008
microsoftwindows server 2012
microsoftwindows server 2016

and 3 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • microsoft windows server 2008all versions
  • microsoft windows server 2008r2
  • microsoft windows server 2012all versions
  • microsoft windows server 2012r2
  • microsoft windows server 2016before 10.0.14393.4470
  • microsoft windows server 2019before 10.0.17763.2029
  • microsoft windows server 2022before 10.0.20348.230
  • microsoft windows server 20h2before 10.0.19042.1083

Versions reported by the vendor

Affected version ranges reported by the assigning authority (microsoft). Independent of NVD's CPE analysis and usually ahead of it.

  • Microsoft Windows 10 Version 1507

    • 10.0.10240.0 and later · before 10.0.10240.18969affected

  • Microsoft Windows 10 Version 1607

    • 10.0.14393.0 and later · before 10.0.14393.4470affected

  • Microsoft Windows 10 Version 1809

    • 10.0.17763.0 and later · before 10.0.17763.2029affected
    • 10.0.0 and later · before 10.0.17763.2029affected

  • Microsoft Windows 10 Version 20H2

    • 10.0.0 and later · before 10.0.19042.1083affected

  • Microsoft Windows 10 Version 21H2

    • 10.0.19044.0 and later · before 10.0.19044.1415affected

  • Microsoft Windows 10 Version 22H2

    • 10.0.19045.0 and later · before 10.0.19045.2251affected

  • Microsoft Windows 11 version 21H2

    • 10.0.22000.0 and later · before 10.0.22000.318affected

  • Microsoft Windows 11 version 22H2

    • 10.0.22621.0 and later · before 10.0.22621.674affected

  • Microsoft Windows 8.1

    • 6.3.0 and later · before 6.3.9600.20046affected

  • Microsoft Windows Server 2008 R2 Service Pack 1

    • 6.1.7601.0 and later · before 6.1.7601.25633affected

  • Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation)

    • 6.1.7601.0 and later · before 6.1.7601.25633affected

  • Microsoft Windows Server 2008 Service Pack 2

    • 6.0.6003.0 and later · before 6.0.6003.21138affected

Same product

microsoft: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-40444Microsoft MSHTML Remote Code Execution VulnerabilityKEV
    94Now
  • CVE-2025-33053Internet Shortcut Files Remote Code Execution VulnerabilityKEV
    91Now
  • CVE-2023-36025Windows SmartScreen Security Feature Bypass VulnerabilityKEV
    91Now

Published before and after this one in the same product

  • ← EarlierCVE-2021-31956Jun 8, 2021 · Windows NTFS Elevation of Privilege VulnerabilityKEV
    68This week
  • ← EarlierCVE-2021-33742Jun 8, 2021 · Windows MSHTML Platform Remote Code Execution VulnerabilityKEV
    78This week
  • Later →CVE-2021-31979Jul 14, 2021 · Windows Kernel Elevation of Privilege VulnerabilityKEV
    62This week

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

  • Metasploit module ×1
  • Proof-of-concept repository on GitHub ×30

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Metasploit moduleexploit/windows/dcerpc/cve_2021_1675_printnightmarePrint Spooler Remote DLL Injectionexploit2021-06-08
Proof-of-concept repository on GitHubstars:02021-07-01
Proof-of-concept repository on GitHubstars:3302021-07-02
Proof-of-concept repository on GitHubstars:02021-07-03
Proof-of-concept repository on GitHubstars:1812021-07-03
Proof-of-concept repository on GitHubstars:22021-07-05
Proof-of-concept repository on GitHubstars:02021-07-05
Proof-of-concept repository on GitHubstars:8032021-07-05
Proof-of-concept repository on GitHubstars:02021-07-07
Proof-of-concept repository on GitHubstars:22021-07-07
Proof-of-concept repository on GitHubstars:02021-07-08
Proof-of-concept repository on GitHubstars:02021-07-08

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Metasploit-25 d
  2. First PoC-2 d
  3. Published
  4. CISA KEV+123 d
  5. TodayNov 11, 2026+1958 d

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records