CVE-2021-34478

Remote code execution via glTF-SDK buffer overflow

Published Aug 12, 2021 · Updated Aug 10, 2026

Microsoft Word glTF-SDK flaw in Microsoft Office 2019 and Microsoft 365 Apps for enterprise allows remote attackers to execute code via malicious files. The glTF-SDK component fails to validate user-supplied data, allowing a write past an allocated buffer and code execution in the Word process. Exploitation requires a user to visit a malicious page or open a malicious file; the advisory reports no preview-pane attack path.

CVSS severity7.8
High
EPSS probability51.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Microsoft Word glTF-SDK flaw in Microsoft Office 2019 and Microsoft 365 Apps for enterprise allows remote attackers to execute code via malicious files. The glTF-SDK component fails to validate user-supplied data, allowing a write past an allocated buffer and code execution in the Word process. Exploitation requires a user to visit a malicious page or open a malicious file; the advisory reports no preview-pane attack path.

The record

CVE
CVE-2021-34478
Published
Aug 12, 2021
Updated
Aug 10, 2026
Vendor
Microsoft
Product
Microsoft Office 2019
Classifications
T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 12, 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=19.0.0 <https://aka.ms/OfficeSecurityReleases

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Microsoft · Microsoft Office 2019version=19.0.0 <https://aka.ms/OfficeSecurityReleases
Microsoft · Microsoft 365 Apps for enterpriseversion=16.0.1 <https://aka.ms/OfficeSecurityReleases

Published CVSS scores

6.8MicrosoftCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
7.8MicrosoftCVSS: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.

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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