CVE-2026-55029
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 allows local code execution by an unauthorized attacker, likely through a specially crafted Excel file that triggers the overflow when opened.
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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Check installed Excel version on WindowsOpen Excel, go to File > Account > About Excel, or run 'excel /?' in Command Prompt, or view the program version in Control Panel > Programs and FeaturesAffected if The version shown is any release of Excel 2016, 2019, 2021, 2024, or Microsoft 365/365 Apps, as all of these are listed as affected
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Check Excel version via PowerShellRun 'Get-ItemProperty HKLM:\Software\Microsoft\Windows\CurrentVersion\App*\Excel* | Select-Object DisplayName, DisplayVersion' or check 'Get-ItemProperty HKLM:\Software\Microsoft\Office\ClickToRun\Configuration' for Microsoft 365 versionsAffected if Any installed version is returned, indicating Excel is present and potentially affected
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Check Microsoft Office Online Server versionIf using Office Online Server, run 'Get-OfficeWebAppsServer' in PowerShell or check the build number via the Office Online Server admin portalAffected if The installed version is lower than 16.0.10417.20175 (versions at or above this are fixed)
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Verify Excel is accessible to open filesConfirm that Excel can open .xlsx or .xls files by attempting to open any existing Excel document, which validates the attack surface existsAffected if Excel successfully opens files, meaning the vulnerability is reachable if a malicious file is opened
A user is affected if they have any version of Microsoft Excel installed (2016, 2019, 2021, 2024, or Microsoft 365) or Office Online Server versions below 16.0.10417.20175, and they open untrusted Excel files.
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.
From vendor data16.0.10417.20175
Apply Microsoft's security updates for Office Excel as they become available; until then, restrict opening Excel files from untrusted sources and consider enabling Protected View in Office settings.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 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 $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-55029 — 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-2026-55029 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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- 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
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