CVE-2026-26107
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 · uneditedUse after free 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 confidenceA Use After Free (UAF) vulnerability exists in Microsoft Office Excel that allows an unauthorized attacker to execute code locally. The UAF occurs when the application continues to use memory after it has been freed, potentially enabling an attacker to manipulate memory and achieve code execution.
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 dataall versions= 2016= 2019= 2021= 2024< 16.0.10417.20102CVSS 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
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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 checksWork through these to decide whether this CVE applies to you.
-
Confirm Excel is installedOpen Control Panel > Programs and Features, or run 'Get-ItemProperty HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall\* | DisplayName' in PowerShell to list installed Office products. Look for Microsoft Excel or Microsoft Office entries.Affected if Microsoft Excel is installed on the system.
-
Determine installed Excel versionOpen Excel, go to File > Account > About Excel, or run 'winword.exe /?' (for Office) to see version. For Office click-to-run, run 'cd /d %ProgramFiles%\Microsoft Office\root\Office* && dir' to find the folder version.Affected if The installed version falls within the affected ranges: Microsoft 365 Apps (all versions), Excel 2016, Office 2019, Office LTSC 2021, Office LTSC 2024, or Office Online Server versions earlier than 16.0.10417.20102.
-
Verify Excel file handling configurationOpen Excel > File > Options > Trust Center > Trust Center Settings > File Block Settings. Check if 'Open' or 'Open and Repair' actions are blocked for untrusted file types.Affected if Excel is configured to open files from untrusted sources (default behavior allows opening, which enables the attack vector).
-
Check for recent security eventsOpen Windows Event Viewer > Security and filter by Event ID 4688 (process creation) looking for excel.exe spawning suspicious processes. Also check Microsoft-Windows-Security-Auditing logs for Excel-related alerts.Affected if Unusual Excel child processes or suspicious activity patterns are present.
The system is affected if Microsoft Excel is installed and the installed version matches the affected Microsoft 365 Apps, Excel 2016, Office 2019, Office LTSC 2021/2024, or Office Online Server versions before 16.0.10417.20102.
Generated from the published advisory. Verify against your own configuration.
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 · scoped16.0.10417.20102
Apply the Microsoft security update for CVE-2026-26107 through Windows Update or the Microsoft Update Catalog. Prioritize patching systems with Excel exposure to untrusted documents.
Microsoft Office updates are released through Windows Update; obtain the specific patch from Microsoft Security Update Guide at msrc.microsoft.com
- Check Microsoft Update or the Microsoft Security Response Center (msrc.microsoft.com) for the specific security bulletin related to this CVE
- Apply the latest Microsoft Office updates through Windows Update or the Microsoft Update Catalog
- Verify the update was successfully installed by checking Office version information
- Restart any Office applications if they were open during the update process
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,832.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-26107 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-26107 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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.
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.
- 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