CVE-2021-42286

Local privilege escalation through undisclosed Core Shell flaw

Published Nov 10, 2021 · Updated Aug 19, 2026

Affected Windows 10 and Windows Server releases allow local users to elevate privileges through the Core Shell SI Host Extension Framework. Microsoft has not published the flawed operation or input path within that framework. Exploitation requires prior local low-privilege access and grants higher privileges, with confidentiality, integrity, and availability consequences.

CVSS severity7.8
High
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Affected Windows 10 and Windows Server releases allow local users to elevate privileges through the Core Shell SI Host Extension Framework. Microsoft has not published the flawed operation or input path within that framework. Exploitation requires prior local low-privilege access and grants higher privileges, with confidentiality, integrity, and availability consequences.

The record

CVE
CVE-2021-42286
Published
Nov 10, 2021
Updated
Aug 19, 2026
Vendor
Microsoft
Product
Windows 10 Version 21H1
Classifications
CWE-269, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.0 <10.0.19043.1348

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows 10 Version 21H1version=10.0.0 <10.0.19043.1348
Microsoft · Windows Server, version 2004version=10.0.0 <10.0.19041.1348
Microsoft · Windows 10 Version 20H2version=10.0.0 <10.0.19042.1348
Microsoft · Windows Server version 20H2version=10.0.0 <10.0.19041.1348
Microsoft · Windows 10 Version 2004version=10.0.0 <10.0.19041.1348

Published CVSS scores

4.6NISTAV:L/AC:L/Au:N/C:P/I:P/A:P
7.8Microsoft CorporationCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-269Improper Privilege Management
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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