CVE-2021-28456 — Microsoft Excel Information Disclosure Vulnerability

Executive Summary

None

Overview

5.5

CVSS MEDIUM

Important

MS Severity

Not Exploited

MS Exploit Status

Less Likely

MS Exploit Likelihood

Category Information Disclosure

Released Apr 13 2021

Last Updated Apr 13 2021

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.03688 — 0.88266 percentile

NVD CVSS 5.5 MEDIUM — matches MSRC

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C

ATTACK VECTOR

Local

ATTACK COMPLEXITY

Low

PRIVILEGES REQUIRED

None

USER INTERACTION

Required

SCOPE

Unchanged

CONFIDENTIALITY

High

INTEGRITY

None

AVAILABILITY

None

EXPLOIT CODE MATURITY

Proof-of-Concept

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 5.0

EPSS Score

0.03688

probability of exploitation in the next 30 days

0.88266 percentile - updated 2026-06-21

View on FIRST.org

Affected Products

14 affected products

Product	KB Article	Severity	Impact	Restart Required
Microsoft 365 Apps for Enterprise for 32-bit Systems	`Click to Run (Security Update)`	Important	Information Disclosure	No
Microsoft 365 Apps for Enterprise for 64-bit Systems	`Click to Run (Security Update)`	Important	Information Disclosure	No
Microsoft Excel 2010 Service Pack 2 (32-bit editions)	`3017810 (Security Update)`	Important	Information Disclosure	Maybe
Microsoft Excel 2010 Service Pack 2 (64-bit editions)	`3017810 (Security Update)`	Important	Information Disclosure	Maybe
Microsoft Excel 2013 RT Service Pack 1	`4504735 (Security Update)`	Important	Information Disclosure	Maybe
Microsoft Excel 2013 Service Pack 1 (32-bit editions)	`4504735 (Security Update)`	Important	Information Disclosure	Maybe
Microsoft Excel 2013 Service Pack 1 (64-bit editions)	`4504735 (Security Update)`	Important	Information Disclosure	Maybe
Microsoft Excel 2016 (32-bit edition)	`4504721 (Security Update)`	Important	Information Disclosure	Maybe
Microsoft Excel 2016 (64-bit edition)	`4504721 (Security Update)`	Important	Information Disclosure	Maybe
Microsoft Office 2019 for 32-bit editions	`Click to Run (Security Update)`	Important	Information Disclosure	No
Microsoft Office 2019 for 64-bit editions	`Click to Run (Security Update)`	Important	Information Disclosure	No
Microsoft Office 2019 for Mac	`Release Notes (Security Update)`	Important	Information Disclosure	No
Microsoft Office Online Server	`4504714 (Security Update)`	Important	Information Disclosure	Maybe
Microsoft Office Web Apps Server 2013 Service Pack 1	`4504729 (Security Update)`	Important	Information Disclosure	Maybe

Patches

7 patches

Article	Type	Restart
`Click to Run`	Security Update	No
`3017810`	Security Update	Maybe
`4504735`	Security Update	Maybe
`4504721`	Security Update	Maybe
`Release Notes`	Security Update	No
`4504714`	Security Update	Maybe
`4504729`	Security Update	Maybe

Known Exploits

No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.

Acknowledgments

Zhangjie and willJ from cdsrc

References

MSRC Advisory MITRE NVD