How severe is CVE-2021-31955?

CVE-2021-31955 has a CVSS score of 5.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-31955?

Affected package information for CVE-2021-31955 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2021-31955?

No fixed version has been published for CVE-2021-31955 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2021-31955 actively exploited in the wild?

Yes. There are 7 known exploit references for CVE-2021-31955, including 6 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-31955?

CVE-2021-31955 has an EPSS (Exploit Prediction Scoring System) score of 3.6%, placing it in the 88th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

Is CVE-2021-31955 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-31955 (Microsoft Windows Kernel Information Disclosure Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03. CISA required all US federal civilian agencies to remediate this vulnerability by 2021-11-17. The required action was: Apply updates per vendor instructions. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2021-31955?

CVE-2021-31955 is classified as CWE-497 (CWE-497). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Which products and versions are affected by CVE-2021-31955?

CVE-2021-31955 affects microsoft windows 10 20h2; microsoft windows 10 21h1; microsoft windows 10 1809; microsoft windows 10 1909, and 4 more product(s). Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2021-31955 published, and has it been updated?

CVE-2021-31955 was published on June 8, 2021 and was last updated on October 30, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2021-11-03 — agencies required to remediate by 2021-11-17

CVE-2021-31955

MEDIUM

Windows Kernel Information Disclosure Vulnerability

Published

Jun 8, 2021

Updated

Oct 30, 2025

Affected

0 pkgs

Patched

None yet

Exploits

7 known

EPSS Exploitation Probability

via FIRST.org ↗

3.6%probability of exploitation in next 30 days

Lower Risk88th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

Windows Kernel Information Disclosure Vulnerability

Affected Products

8 products · 8 configurations

windows 10 20h2microsoft

< 10.0.19042.1052

range

windows 10 21h1microsoft

< 10.0.19043.1052

range

windows 10 1809microsoft

< 10.0.17763.1999

range

windows 10 1909microsoft

< 10.0.18363.1621

range

windows 10 2004microsoft

< 10.0.19041.1052

range

windows server 20h2microsoft

< 10.0.19042.1052

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Windows Kernel Information Disclosure Vulnerability

portal.msrc.microsoft.comMSJun 2021

Windows Kernel Information Disclosure Vulnerability

msrc.microsoft.comGoogle-sheetApr 2021

Windows Kernel Information Disclosure Vulnerability

github.comGithubJun 2021

Windows Kernel Information Disclosure Vulnerability

github.comGithubJun 2021

Windows Kernel Information Disclosure Vulnerability

cisa.govCISANov 2021

Windows Kernel Information Disclosure Vulnerability

github.comGithubJun 2021

Frequently Asked Questions

Windows Kernel Information Disclosure Vulnerability

O3 Security · Impact-Aware SCA

Is CVE-2021-31955 in your stack?

O3 detects CVE-2021-31955 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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