CVE-2021-31955 — Windows Kernel Information Disclosure Vulnerability

Executive Summary

None

Overview

5.5

CVSS MEDIUM

Important

MS Severity

Exploited

MS Exploit Status

Exploitation Detected

MS Exploit Likelihood

Category Information Disclosure

Released Jun 8 2021

Last Updated Jun 8 2021

Publicly Disclosed No

CISA KEV Listed (added 2021-11-03)

Known Exploits None Known

EPSS Score 0.81107 — 0.99599 percentile

NVD CVSS 5.5 MEDIUM — matches MSRC

CVSS Vector

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

ATTACK VECTOR

Local

ATTACK COMPLEXITY

Low

PRIVILEGES REQUIRED

Low

USER INTERACTION

None

SCOPE

Unchanged

CONFIDENTIALITY

High

INTEGRITY

None

AVAILABILITY

None

EXPLOIT CODE MATURITY

Functional

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 5.1

EPSS Score

0.81107

probability of exploitation in the next 30 days

0.99599 percentile - updated 2026-08-14

View on FIRST.org

Affected Products

18 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 Version 1809 for 32-bit Systems	`5003646 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 1809 for ARM64-based Systems	`5003646 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 1809 for x64-based Systems	`5003646 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 1909 for 32-bit Systems	`5003635 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 1909 for ARM64-based Systems	`5003635 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 1909 for x64-based Systems	`5003635 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 2004 for 32-bit Systems	`5003637 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 2004 for ARM64-based Systems	`5003637 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 2004 for x64-based Systems	`5003637 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 20H2 for 32-bit Systems	`5003637 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 20H2 for ARM64-based Systems	`5003637 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 21H1 for 32-bit Systems	`5003637 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 21H1 for ARM64-based Systems	`5003637 (Security Update)`	Important	Information Disclosure	Yes
Windows 10 Version 21H1 for x64-based Systems	`5003637 (Security Update)`	Important	Information Disclosure	Yes
Windows Server 2019	`5003646 (Security Update)`	Important	Information Disclosure	Yes
Windows Server 2019 (Server Core installation)	`5003646 (Security Update)`	Important	Information Disclosure	Yes
Windows Server, version 2004 (Server Core installation)	`5003637 (Security Update)`	Important	Information Disclosure	Yes
Windows Server, version 20H2 (Server Core Installation)	`5003637 (Security Update)`	Important	Information Disclosure	Yes

Patches

3 patches

Article	Type	Restart
`5003646`	Security Update	Yes
`5003635`	Security Update	Yes
`5003637`	Security Update	Yes

Exploits & PoC

2 public PoCs

Unverified third-party code

Public proof-of-concept repositories aggregated from PoC-in-GitHub. They are not reviewed and may be incomplete, non-functional, or malicious — inspect the code before running anything.

Repository	Stars	Published	Description
freeide/CVE-2021-31955-POC	11	2021-06-26
ApexPredator-InfoSec/forti_shield	2	2025-10-29	A combined POC for CVE-2021-31955, CVE-2015-4077, and CVE-2015-5736

Detection Rules

No public Sigma or Nuclei detection rule has been mapped to this CVE yet. Coverage is concentrated on exploited / high-profile vulnerabilities; check SigmaHQ for updates.

Acknowledgments

Boris Larin ( oct0xor

References

MSRC Advisory MITRE NVD