CVE-2021-26900Public exploit

Kernel code execution via stale DirectComposition object

Published Mar 11, 2021 · Updated Aug 19, 2026

Use-after-free in DirectComposition in affected Microsoft Windows releases allows local users to execute arbitrary code in the kernel. CInteractionTrackerMarshaler performs operations on an object without first validating that the object still exists. Exploitation requires low-privileged code execution on the target and yields kernel-context code execution.

CVSS severity8.8
High
EPSS probability2.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in DirectComposition in affected Microsoft Windows releases allows local users to execute arbitrary code in the kernel. CInteractionTrackerMarshaler performs operations on an object without first validating that the object still exists. Exploitation requires low-privileged code execution on the target and yields kernel-context code execution.

The record

CVE
CVE-2021-26900
Published
Mar 11, 2021
Updated
Aug 19, 2026
Vendor
Microsoft
Product
Windows 10 Version 1909
Classifications
CWE-416, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 11, 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

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Is a vulnerable build present?

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

  1. Affected versionversion=10.0.0 <10.0.18363.1440

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows 10 Version 1909version=10.0.0 <10.0.18363.1440
Microsoft · Windows Server, version 2004version=10.0.0 <10.0.19043.867
Microsoft · Windows 10 Version 20H2version=10.0.0 <10.0.19043.867
Microsoft · Windows Server version 20H2version=10.0.0 <10.0.19043.867
Microsoft · Windows 10 Version 2004version=10.0.0 <10.0.19043.867
Microsoft · Windows Server, version 1909 (Server Core installation)version=10.0.0 <10.0.18363.1440

Published CVSS scores

8.8Zero Day InitiativeCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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 exploitPublished

Weakness, pattern, technique

CWE-416Use After Free
T1068Exploitation for Privilege Escalation

Public exploit references

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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