CVE-2021-42292Known exploitation

Code execution via nested spreadsheet download

Published Nov 10, 2021 · Updated Aug 19, 2026

Security feature bypass in Microsoft Excel allows context-dependent attackers to execute code through a crafted spreadsheet. Excel processes the triggering spreadsheet by downloading a second spreadsheet and executing its malicious code with elevated privileges. A user must open the initial file, after which the exploit can compromise data and interrupt the affected host.

CVSS severity7.8
High
EPSS probability43.00%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Security feature bypass in Microsoft Excel allows context-dependent attackers to execute code through a crafted spreadsheet. Excel processes the triggering spreadsheet by downloading a second spreadsheet and executing its malicious code with elevated privileges. A user must open the initial file, after which the exploit can compromise data and interrupt the affected host.

The record

CVE
CVE-2021-42292
Published
Nov 10, 2021
Updated
Aug 19, 2026
Vendor
Microsoft
Product
Microsoft Office 2016
Classifications
CWE-357, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 17, 2021Exploitation reportedCISA Known Exploited Vulnerabilities listing
  3. 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=16.0.0 <16.0.5239.1001

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Microsoft · Microsoft Office 2016version=16.0.0 <16.0.5239.1001
Microsoft · Microsoft Office 2019version=19.0.0 <https://aka.ms/OfficeSecurityReleases
Microsoft · Microsoft Excel 2016version=16.0.0.0 <16.0.5239.1001
Microsoft · Microsoft Office LTSC for Mac 2021version=16.0.1 <16.55.21111400
Microsoft · Microsoft Office 2013version=15.0.0 <15.0.5397.1001
Microsoft · Microsoft Excel 2013version=15.0.0.0 <15.0.5397.1001
Microsoft · Microsoft Office 2019 for Macversion=16.0.0 <16.55.21111400
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

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
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 exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-357Insufficient UI Warning of Dangerous Operations
T1204.002User Execution: Malicious File

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.

Reported exploitation

Technologies

Your stack

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Your stack

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