CVE-2026-55947
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 · uneditedHeap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
In the news
Third-party coverage- Microsoft July 2026 Patch Tuesday fixes massive 570 flaws, 3 zero-days
- Microsoft CVE Summary - Bleeping Computer
Surfaced from public web coverage — external links open in a new tab.
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 confidenceHeap-based buffer overflow vulnerability in Microsoft Office Excel that allows an unauthorized attacker to execute code locally with elevated privileges. The vulnerability stems from improper memory handling when processing specially crafted Excel files.
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= 2016all versionsall versionsall versionsall versions< 16.0.10417.20175CVSS 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.
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Verify Excel is installedOpen Excel, go to File > Account > About Excel, or run 'winword --version' or check Add/Remove Programs for Microsoft ExcelAffected if Excel is not found on the system, the vulnerability does not apply
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Determine Excel desktop application versionIn Excel, click File > Account > About Excel, or open Command Prompt and run: reg query 'HKLM\SOFTWARE\Microsoft\Office\ClickToRun\Configuration' /v VersionToReport (for Microsoft 365/Office 2016+) or check Help > About in older versionsAffected if Version is 2016 or later, or is Microsoft 365 Apps, or Office 2019/2021/2024 (all versions are affected)
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Check Office Online Server version (if applicable)For Office Online Server, run: Get-OfficeOnlineServerVersion or check registry: HKLM\SOFTWARE\Microsoft\Office Online Server\Install\VersionAffected if Version is lower than 16.0.10417.20175 (if using Office Online Server)
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Confirm vulnerability trigger conditionThis vulnerability requires a user to open a specially crafted malicious Excel file. Check if users handle untrusted file attachments by reviewing email filtering or endpoint protection policies.Affected if Users can open Excel files from untrusted sources without additional validation
The system is affected if Excel 2016 or later, Microsoft 365 Apps, Office 2019/2021/2024, or Office Online Server version below 16.0.10417.20175 is installed AND users can open Excel files from untrusted sources.
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 · scoped16.0.10417.20175
Apply Microsoft security updates for Office Excel as they become available. Organizations should patch affected Excel installations and consider disabling macros and restricting file来源 to mitigate risk until patches are deployed.
Apply the latest Microsoft Office security updates via Windows Update or Microsoft Update Catalog (specific KB number depends on CVE release date)
- Check for Microsoft Office updates via Windows Update or the Microsoft Update Catalog
- Verify the installed Excel version by opening Excel and navigating to File > Account > About Excel
- Apply all available security updates for Microsoft Office, specifically those addressing Excel vulnerabilities
- After applying updates, restart the computer and verify the update was successful through Windows Update history
- For Office Online Server deployments, apply the update version 16.0.10417.20175 or later
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-55947 — 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-2026-55947 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
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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