CVE-2021-43255

Content spoofing through undisclosed Trust Center flaw

Published Dec 15, 2021 · Updated Aug 4, 2024

Spoofing in Microsoft Office 2013, 2016, 2019, LTSC 2021, and Microsoft 365 Apps allows local users to alter trusted content. Microsoft has not published the affected Trust Center locus or the operation that mishandles attacker-controlled content. Exploitation requires a user to interact with the attack mechanism; no confidentiality or availability impact is reported.

CVSS severity5.5
Medium
EPSS probability1.98%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Spoofing in Microsoft Office 2013, 2016, 2019, LTSC 2021, and Microsoft 365 Apps allows local users to alter trusted content. Microsoft has not published the affected Trust Center locus or the operation that mishandles attacker-controlled content. Exploitation requires a user to interact with the attack mechanism; no confidentiality or availability impact is reported.

The record

CVE
CVE-2021-43255
Published
Dec 15, 2021
Updated
Aug 4, 2024
Vendor
Microsoft
Product
Microsoft Office 2016
Classifications
Unavailable
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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=16.0.0 <16.0.5254.1001

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Microsoft · Microsoft Office 2016version=16.0.0 <16.0.5254.1001
Microsoft · Microsoft Office 2019version=19.0.0 <https://aka.ms/OfficeSecurityReleases
Microsoft · Microsoft Office 2013version=15.0.0 <15.0.5407.1000
Microsoft · Microsoft Office LTSC 2021version=16.0.1 <https://aka.ms/OfficeSecurityReleases
Microsoft · Microsoft 365 Apps for enterpriseversion=16.0.1 <https://aka.ms/OfficeSecurityReleases

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
5.5Microsoft CorporationCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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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