CVE-2023-21716Public exploitNetwork attack vector

Remote code execution via RTF font-table overflow

Published Feb 14, 2023 · Updated Aug 19, 2026

Heap corruption in Microsoft Word and Office products allows remote attackers to execute code through a crafted RTF document. The wwlib RTF parser uses overflowing integer arithmetic while indexing an excessive font table, causing writes outside its allocated heap buffer. Preview Pane rendering can reach the flaw, and successful exploitation runs code with the privileges of the affected application or service.

CVSS severity9.8
Critical
EPSS probability82.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap corruption in Microsoft Word and Office products allows remote attackers to execute code through a crafted RTF document. The wwlib RTF parser uses overflowing integer arithmetic while indexing an excessive font table, causing writes outside its allocated heap buffer. Preview Pane rendering can reach the flaw, and successful exploitation runs code with the privileges of the affected application or service.

The record

CVE
CVE-2023-21716
Published
Feb 14, 2023
Updated
Aug 19, 2026
Vendor
Microsoft
Product
Microsoft SharePoint Foundation 2013
Classifications
CWE-190, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 14, 2023CVE 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=15.0.0 <15.0.5529.1000

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Microsoft SharePoint Foundation 2013version=15.0.0 <15.0.5529.1000
Microsoft · Microsoft Office 2019version=19.0.0 <https://aka.ms/OfficeSecurityReleases
Microsoft · Microsoft SharePoint Enterprise Server 2016version=16.0.0 <16.0.5383.1000
Microsoft · Microsoft Office LTSC for Mac 2021version=16.0.1 <16.70.23021201
Microsoft · Microsoft SharePoint Enterprise Server 2013version=15.0.0 <15.0.5529.1000
Microsoft · Microsoft SharePoint Server 2019version=16.0.0 <16.0.10395.20001
Microsoft · Microsoft SharePoint Server Subscription Edition Language Packversion=16.0.0 <16.0.15601.20478
Microsoft · Microsoft Office 2019 for Macversion=16.0.0 <16.70.23021201
Microsoft · Microsoft Office LTSC 2021version=16.0.1 <https://aka.ms/OfficeSecurityReleases
Microsoft · Microsoft Office Online Serverversion=16.0.1 <16.0.10395.20001
Microsoft · Microsoft Word 2013version=15.0.1 <15.0.5529.1000
Microsoft · Microsoft Word 2016version=16.0.1 <16.0.5383.1000
Microsoft · Microsoft Office Web Apps Server 2013version=15.0.1 <15.0.5529.1000
Microsoft · Microsoft SharePoint Server Subscription Editionversion=16.0.0 <16.0.15601.20478
Microsoft · Microsoft 365 Apps for enterpriseversion=16.0.1 <https://aka.ms/OfficeSecurityReleases

Published CVSS scores

9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1203Exploitation for Client Execution

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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