CVE-2021-27047

Code execution via crafted HEVC file

Published Mar 11, 2021 · Updated Aug 19, 2026

Remote code execution in Microsoft HEVC Video Extensions before 1.0.40204.0 allows remote attackers to execute code via a crafted video file. Microsoft has not published the decoder component or operation responsible for the flaw, so the precise parsing mistake remains undisclosed. Exploitation requires a user to obtain and open or preview malicious HEVC content in an application using the extension, after which attacker-controlled code can run with that application's privileges.

CVSS severity7.8
High
EPSS probability2.68%
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 Microsoft HEVC Video Extensions before 1.0.40204.0 allows remote attackers to execute code via a crafted video file. Microsoft has not published the decoder component or operation responsible for the flaw, so the precise parsing mistake remains undisclosed. Exploitation requires a user to obtain and open or preview malicious HEVC content in an application using the extension, after which attacker-controlled code can run with that application's privileges.

The record

CVE
CVE-2021-27047
Published
Mar 11, 2021
Updated
Aug 19, 2026
Vendor
Microsoft
Product
HEVC Video Extensions
Classifications
T1203
Attack vector
local
Privileges
unauthenticated

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=1.0.0 <1.0.40204.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Microsoft · HEVC Video Extensionsversion=1.0.0 <1.0.40204.0

Published CVSS scores

6.8NISTAV:N/AC:M/Au:N/C:P/I:P/A:P
7.8Microsoft CorporationCVSS:3.1/AV:L/AC:L/PR:N/UI:R/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.

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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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