# CVE-2021-34527: Microsoft Windows Print Spooler Remote Code Execution

> Attackers can execute arbitrary code with SYSTEM privileges via the Windows Print Spooler service, requiring immediate patching.

- **Severity:** High 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`)
- **Exploited in the wild:** Yes, since 3 Nov 2021 (CISA KEV), used in ransomware
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Jul 2021
- **Updated:** 10 Aug 2026
- **Also known as:** GHSA-75f9-mm5v-2rgm

## What is CVE-2021-34527?

CVE-2021-34527 is a high-severity vulnerability in Microsoft Windows 10 1507, published on 2 Jul 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

## Which versions are affected by CVE-2021-34527?

It affects 15 products.


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 11 21h2, Microsoft Windows 11 22h2, Microsoft Windows Rt 8.1, Microsoft Windows Server 2008, Microsoft Windows Server 2012, Microsoft Windows Server 2016, Microsoft Windows Server 2019, Microsoft Windows Server 2022, Microsoft Windows Server 20h2.

## How do I fix CVE-2021-34527?

No fix has been published for CVE-2021-34527 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 3 May 2022.

## Is CVE-2021-34527 being exploited?

Yes. Attackers have exploited CVE-2021-34527 in the wild since at least 3 Nov 2021, including in ransomware campaigns.

Public exploit code:

- A PrintNightmare (CVE-2021-34527) Python Scanner. Scan entire subnets for hosts vulnerable to the PrintNightmare RCE (github_poc): https://github.com/byt3bl33d3r/ItWasAllADream
- https://github.com/JohnHammond/CVE-2021-34527 (github_poc): https://github.com/JohnHammond/CVE-2021-34527
- PrintNightmare - Windows Print Spooler RCE/LPE Vulnerability (CVE-2021-34527, CVE-2021-1675) proof of concept exploits (github_poc): https://github.com/nemo-wq/PrintNightmare-CVE-2021-34527
- PrintNightmare (CVE-2021-34527) PoC Exploit (github_poc): https://github.com/m8sec/CVE-2021-34527
- CVE-2021-34527 AddPrinterDriverEx() Privilege Escalation (github_poc): https://github.com/hackerhouse-opensource/cve-2021-34527
- https://github.com/dywhoami/CVE-2021-34527-Scanner-Based-On-cube0x0-POC (github_poc): https://github.com/dywhoami/CVE-2021-34527-Scanner-Based-On-cube0x0-POC

## Other vulnerabilities in Microsoft Windows 10 1507

- [CVE-2017-8543](https://insights.sbomify.com/CVE-2017-8543/): Microsoft Windows Search Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2025-33053](https://insights.sbomify.com/CVE-2025-33053/): Microsoft Windows External Control of File Name or Path (high 8.8, exploited in the wild)
- [CVE-2025-33073](https://insights.sbomify.com/CVE-2025-33073/): Microsoft Windows SMB Client Improper Access Control (high 8.8, exploited in the wild)
- [CVE-2024-49039](https://insights.sbomify.com/CVE-2024-49039/): Microsoft Windows Task Scheduler Privilege Escalation (high 8.8, exploited in the wild)
- [CVE-2024-43461](https://insights.sbomify.com/CVE-2024-43461/): Microsoft Windows MSHTML Platform Spoofing (high 8.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34527 and fix it if it is affected.

What it is: CVE-2021-34527 is a high-severity vulnerability in Microsoft Windows 10 1507, published on 2 Jul 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2021-34527 in the wild since at least 3 Nov 2021, including in ransomware campaigns.

Affected product: Microsoft Windows 10 1507. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-34527/ (Markdown: https://insights.sbomify.com/CVE-2021-34527/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34527
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34527
- OSV: https://osv.dev/vulnerability/CVE-2021-34527

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-34527/
Summaries are generated and may contain mistakes; the official description above is the record.