CVE-2021-34439

Code execution through undisclosed media-processing flaw

Published Jul 16, 2021 · Updated Aug 10, 2026

Remote code execution in Windows Media Foundation allows attackers to execute code on Windows 10 and Windows Server 2016. Microsoft has not published the affected function, unsafe operation, or input format that triggers the Media Foundation flaw. Affected builds are before 10.0.10240.19003 for Windows 10 Version 1507 and before 10.0.14393.4530 for Version 1607 and Server 2016; user interaction is required.

CVSS severity7.8
High
EPSS probability2.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Remote code execution in Windows Media Foundation allows attackers to execute code on Windows 10 and Windows Server 2016. Microsoft has not published the affected function, unsafe operation, or input format that triggers the Media Foundation flaw. Affected builds are before 10.0.10240.19003 for Windows 10 Version 1507 and before 10.0.14393.4530 for Version 1607 and Server 2016; user interaction is required.

The record

CVE
CVE-2021-34439
Published
Jul 16, 2021
Updated
Aug 10, 2026
Vendor
Microsoft
Product
Windows 10 Version 1507
Classifications
T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 10, 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=10.0.10240.0 <10.0.10240.19003

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Microsoft · Windows 10 Version 1507version=10.0.10240.0 <10.0.10240.19003
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.4530
Microsoft · Windows Server 2016version=10.0.14393.0 <10.0.14393.4530
Microsoft · Windows 10 Version 1607version=10.0.14393.0 <10.0.14393.4530

Published CVSS scores

7.8NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
7.8MicrosoftCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
9.3NVDAV:N/AC:M/Au:N/C:C/I:C/A:C

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1203Exploitation for Client Execution

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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