# CVE-2021-31955: Microsoft Windows Kernel Information Disclosure

> An attacker can exploit a flaw in the Windows Kernel to disclose sensitive information, potentially aiding further attacks.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:F/RL:O/RC:C`)
- **Exploited in the wild:** Yes, since 3 Nov 2021 (CISA KEV)
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 Jun 2021
- **Updated:** 21 Oct 2025
- **Also known as:** GHSA-4grg-84cr-6c2h

## What is CVE-2021-31955?

CVE-2021-31955 is a medium-severity vulnerability in Microsoft Windows 10 1809, published on 8 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Windows Kernel Information Disclosure Vulnerability

Weakness: CWE-497 (Exposure of Sensitive System Information to an Unauthorized Control Sphere)

## Which versions are affected by CVE-2021-31955?

It affects 8 products.


Products: Microsoft Windows 10 1809, Microsoft Windows 10 1909, Microsoft Windows 10 2004, Microsoft Windows 10 20h2, Microsoft Windows 10 21h1, Microsoft Windows Server 2004, Microsoft Windows Server 2019, Microsoft Windows Server 20h2.

## How do I fix CVE-2021-31955?

No fix has been published for CVE-2021-31955 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 17 Nov 2021.

## Is CVE-2021-31955 being exploited?

Yes. Attackers have exploited CVE-2021-31955 in the wild since at least 3 Nov 2021.

Public exploit code:

- https://github.com/freeide/CVE-2021-31955-POC (github_poc): https://github.com/freeide/CVE-2021-31955-POC
- A combined POC for CVE-2021-31955,  CVE-2015-4077, and CVE-2015-5736 (github_poc): https://github.com/ApexPredator-InfoSec/forti_shield

## Other vulnerabilities in Microsoft Windows 10 1809

- [CVE-2024-29988](https://insights.sbomify.com/CVE-2024-29988/): Microsoft SmartScreen Prompt Security Feature Bypass (high 8.8, exploited in the wild)
- [CVE-2024-21412](https://insights.sbomify.com/CVE-2024-21412/): Microsoft Windows Internet Shortcut Files Security Feature Bypass (high 8.1, exploited in the wild)
- [CVE-2025-62221](https://insights.sbomify.com/CVE-2025-62221/): Microsoft Windows Use After Free (high 7.8, exploited in the wild)
- [CVE-2025-30400](https://insights.sbomify.com/CVE-2025-30400/): Microsoft Windows DWM Core Library Use-After-Free (high 7.8, exploited in the wild)
- [CVE-2024-21338](https://insights.sbomify.com/CVE-2024-21338/): Microsoft Windows Kernel Exposed IOCTL with Insufficient Access Control (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-31955 and fix it if it is affected.

What it is: CVE-2021-31955 is a medium-severity vulnerability in Microsoft Windows 10 1809, published on 8 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2021-31955 in the wild since at least 3 Nov 2021.

Affected product: Microsoft Windows 10 1809. 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-2021-31955/ (Markdown: https://insights.sbomify.com/CVE-2021-31955/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-31955
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-31955
- OSV: https://osv.dev/vulnerability/CVE-2021-31955

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-31955/
Summaries are generated and may contain mistakes; the official description above is the record.