Is CVE-2021-31955 being actively exploited?

Yes. CVE-2021-31955 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added on November 3, 2021.

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

CVE-2021-31955 has a CVSS 3.1 base score of 5.5 (MEDIUM).

CVE-2021-31955

MEDIUM · CVSS 5.5CISA KEV: actively exploitedEPSS 81.1%EU EUVD: exploited

Windows Kernel Information Disclosure Vulnerability

Key facts

CVSS score: 5.5 (v3.1)
Severity: MEDIUM
CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Weakness (CWE): CWE-497
EPSS score: 81.1% (100th percentile)
In CISA KEV: Yes, added November 3, 2021
In EU EUVD: Yes (EUVD-2021-18828)
Published: June 8, 2021
NVD last modified: June 17, 2026
Status: Analyzed

CISA Known Exploited Vulnerability

Microsoft Windows Kernel Information Disclosure Vulnerability

Added to the KEV catalog on November 3, 2021; federal remediation due November 17, 2021.

EU Vulnerability Database (EUVD)

This vulnerability is also tracked by ENISA as EUVD-2021-18828 in the EU Vulnerability Database. ENISA flags it as known exploited. Last updated in EUVD on October 21, 2025.

View on the EU Vulnerability Database

Affected 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

Certified products that may be affected

2 FIPS 140 or Common Criteria certified products, from automated matching by sec-certs.org.

Microsoft Windows 10 version 2004 (May 2020 Update), Microsoft Windows Server version 2004 (May 2020 Update) and others - Microsoft Corporation - Common Criteria 2020-50-INF-3671 - active
Microsoft Windows 10 version 1909 and Microsoft Windows Server version 1909 - Microsoft Corporation - Common Criteria 2019-47-INF-3134 - archived

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31955(Patch, Vendor Advisory)
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31955(US Government Resource)

Last updated September 17, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS

Query CVEs from your AI assistant

The CVE/NVD Explorer brain answers CVE questions directly inside Claude, ChatGPT, or any MCP assistant — always up to date, no setup. Add it once and stop pasting advisories into chat.

Add the CVE brain