CVE-2021-38659

Remote code execution via PPT double-free

Published Sep 15, 2021 · Updated Aug 10, 2026

Remote code execution in Microsoft 365 Apps for enterprise before the fixed release allows remote attackers to execute code through a crafted PowerPoint file. The PowerPoint PPT parser frees an object without validating that the object still exists, creating a double-free condition that enables code execution in the current process. Exploitation requires a user to open a malicious file or visit a page that delivers it, and code runs with the current user's privileges.

CVSS severity7.8
High
EPSS probability6.31%
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 365 Apps for enterprise before the fixed release allows remote attackers to execute code through a crafted PowerPoint file. The PowerPoint PPT parser frees an object without validating that the object still exists, creating a double-free condition that enables code execution in the current process. Exploitation requires a user to open a malicious file or visit a page that delivers it, and code runs with the current user's privileges.

The record

CVE
CVE-2021-38659
Published
Sep 15, 2021
Updated
Aug 10, 2026
Vendor
Microsoft
Product
Microsoft 365 Apps for enterprise
Classifications
T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 15, 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=16.0.1 <https://aka.ms/OfficeSecurityReleases

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

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

Published CVSS scores

7.8[email protected]CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8[email protected]AV:N/AC:M/Au:N/C:P/I:P/A:P
7.8[email protected]CVSS: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.

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Technologies

Your stack

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Your stack

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