dbcve.org
365 AppsApplication · Microsoft

CVE-2026-26109

HIGH · 7.8 CVSS v3.1 Published 2026-03-10
Fix available
A fix is available. Upgrade to 16.0.10417.20102 or later.
See remediation →
80/100
Remediation priority · High
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

An out-of-bounds read vulnerability in Microsoft Office Excel allows a local attacker to achieve code execution. The vulnerability results from insufficient bounds checking when Excel processes certain data structures, potentially enabling memory corruption that can be leveraged for arbitrary code execution.

MitigationApply Microsoft security updates for Excel as they become available through standard patch management processes.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
365 AppsApplication
Affected:all versions
ExcelApplication
Affected:= 2016
OfficeApplication
Affected:= 2019
Office Long Term Servicing ChannelApplication
Affected:= 2021= 2024
Office Online ServerApplication
Affected:< 16.0.10417.20102

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Excel version
    Open Excel, go to File > Account > About Excel, or right-click excel.exe in Program Files/Microsoft Office and view Properties > Details > File Version
    Affected if Version shows 2016, 2019, 2021, or 2024, or version begins with a year (e.g., 16.0.xxxx) and is not the patched build
  2. Check Microsoft Office version
    Open any Office app (Word, Excel, PowerPoint), go to File > Account > About [App], or open the Office app and go to File > Account
    Affected if Office version shows 2016, 2019, 2021, or 2024, or version is listed as a specific year-based release
  3. Check Microsoft 365 Apps version
    Open any Office app, go to File > Account, look for 'Update Options' or version information under Account; alternatively, run 'Get-AppxPackage Microsoft.Office' in PowerShell on Windows
    Affected if Any Microsoft 365 Apps version is installed (includes current perpetual and subscription versions)
  4. Check Office Online Server version
    Open SharePoint Management Shell or use PowerShell: Get-OfficeOnlineServerMachine on the server, or check the version via Office Online Server admin portal
    Affected if Version is lower than 16.0.10417.20102

You are affected if Excel 2016, Office 2019, Office LTSC 2021, Office LTSC 2024, any Microsoft 365 Apps version, or Office Online Server versions below 16.0.10417.20102 is installed on your system.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 16.0.10417.20102 or later
Fixed in 16.0.10417.20102
Interim mitigation

Apply Microsoft security updates for Excel as they become available through standard patch management processes.

Recommended fix Moderate confidence

Microsoft 365 Apps: Latest version via Update Channels; Office Online Server: 16.0.10417.20102 or later

  1. Open Microsoft Excel and go to File > Account > Update Options > Update Now to check for and install the latest Microsoft Office updates
  2. Alternatively, navigate to Microsoft Update (https://update.microsoft.com) and run a scan to install all pending security updates
  3. For Office Online Server, upgrade to version 16.0.10417.20102 or later by installing the latest cumulative update from the Microsoft Update Catalog or using the Office Online Server update installer
Caveat Standard Microsoft update process; minimal risk for security patches

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in 365 Apps Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,210
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,936.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-26109 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-26109 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data