IRONSMITHINTEL
HIGHCVSS7.6
|
Actively Exploited
|CISA KEV|CVE-2021-27059|Auth: high — administrative privileges|Reboot: required|Manual only

KB4493225: Windows Server Security Update (March 2021)

Microsoft Office contains an unspecified vulnerability that allows for remote code execution.

Published Mar 11, 2021 · Updated May 16, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

A remote attacker, with administrative privileges, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. Federal agencies are required to remediate by 2021-11-17 under CISA BOD 22-01.

How the attack worksNo clicks needed

This vulnerability affects Microsoft Office. Exploitation requires remote network access, higher attack complexity, an administrative account, and user interaction required.

Am I affected?Quick check

Probably yes if any of these apply:

●IT Security
●Running office: 2010, 2013, 2016
Fixed inKB4493225, KB4493228, KB4504703 (applies to 7 product versions)
Real-world incidentsWhat we've seen

CISA added this CVE to the Known Exploited Vulnerabilities catalog on 2021-11-03 based on evidence of active exploitation in the wild. Federal agencies required to remediate by 2021-11-17.

How to patch

Manual download

For air-gapped servers or out-of-band deployment. Microsoft Update Catalog returns every OS-version variant of this update.

↗ Microsoft Update CatalogKB4493225

Manual remediation steps

Apply the Microsoft Security Update

Microsoft has released an official security update that fixes this vulnerability.

Required KB Updates

    1
    KB4493225 — https://support.microsoft.com/help/4493225
    1
    KB4493228 — https://support.microsoft.com/help/4493228
    1
    KB4504703 — https://support.microsoft.com/help/4504703

Supersedes: KB4484466, KB4484469, KB4486698

Affected Products

    1
    Microsoft Office 2010 Service Pack 2 (32-bit editions)
    1
    Microsoft Office 2010 Service Pack 2 (64-bit editions)
    1
    Microsoft Office 2013 RT Service Pack 1
    1
    Microsoft Office 2013 Service Pack 1 (32-bit editions)
    1
    Microsoft Office 2013 Service Pack 1 (64-bit editions)
    1
    Microsoft Office 2016 (32-bit edition)
    1
    Microsoft Office 2016 (64-bit edition)

Installation Methods

Windows Update (recommended)

1
Settings → Windows Update → Check for updates
2
The security update is offered if your system is in scope
3
Restart when prompted (may or may not be required for this update)

Microsoft Update Catalog (manual download)

1
Open https://catalog.update.microsoft.com
2
Search for KB4493225
3
Download the package matching your OS architecture and Windows build
4
Run the .msu installer with administrator privileges
5
Restart when prompted

WSUS / SCCM / Intune

Approve KB4493225 for the affected products in your update management console.

Microsoft Download Center Links

    1
    https://www.microsoft.com/downloads/details.aspx?familyid=28ccc9d0-846d-485c-8841-fc0f93c7266a
    1
    https://www.microsoft.com/downloads/details.aspx?familyid=37536dff-a146-4d8d-bf9e-b5ea32ee5d69
    1
    https://www.microsoft.com/downloads/details.aspx?familyid=ab0c19be-f5b6-4320-b5e9-6b36d1430edb
    1
    https://www.microsoft.com/downloads/details.aspx?familyid=baa4cc31-967a-4626-b92f-7f3d2d13f742
    1
    https://www.microsoft.com/downloads/details.aspx?familyid=f06bdfa6-4b65-43b2-b550-a2acc8e6b998
    1
    (…1 more)

Verification

Confirm the update is installed:

Get-HotFix | Where-Object { $_.HotFixID -in @('KB4493225','KB4493228','KB4504703') }

References

    1
    Microsoft Security Response Center: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-27059
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2021-27059
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27059

Discovery Credit

Chi-Yu You and Dhanesh Kizhakkinan of FireEye Inc.

PowerShell automationComing soon

No tested PowerShell script for this entry yet. We’re prioritising automation based on user demand.

References

↗ CVE-2021-27059↗ MSRC Advisory↗ NVD↗ KBKB4493225