CVE-2026-56156
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. The vulnerability involves memory corruption in Excel's parsing of specially crafted files, enabling arbitrary code execution with the current user's privileges.
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 versionsall versionsall versionsall versionsCVSS 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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Confirm Microsoft Excel is installedCheck for Excel executable in typical locations (C:\Program Files\Microsoft Office\, C:\Program Files (x86)\Microsoft Office\) or query the Windows Registry under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\EXCEL.EXEAffected if Excel executable is found on the system
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Identify the installed Excel versionOpen Excel, go to File > Account > About Excel, or run 'winword.exe /?' from command line if Excel path is known, or check registry value 'Version' under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\ClickToRun\Configuration or the App Paths registry keyAffected if Version belongs to Microsoft 365 Apps, Microsoft 365, Office 2021, or Office 2024 product lines
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Verify the file parsing component is presentConfirm the Excel application core files (like excel.exe, Excelcnv.exe for conversion) exist in the installation directory - these handle .xlsx, .xls, and other spreadsheet file parsingAffected if Excel core parsing binaries are present and functional
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Determine if file association handlers are activeCheck Windows file type associations for .xlsx, .xls, .xlsm files pointing to the installed Excel executable, or verify Excel is set as default handler via Default Apps settingsAffected if Excel is registered as a handler for spreadsheet file types
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Assess exposure to untrusted filesReview whether the system or user routinely opens Excel attachments from email, downloads from the internet, or files from external/removable mediaAffected if Users can open or Excel automatically processes spreadsheet files from untrusted or external sources
The environment is affected if Microsoft Excel (any version from Microsoft 365 Apps, Microsoft 365, Office 2021, or Office 2024) is installed and the system can open or process spreadsheet files, since all current versions contain the vulnerability until a security patch is released.
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 dataApply Microsoft security updates for Excel when released. Until then, exercise caution with untrusted Excel files and ensure endpoint protection is active.
- Consultation2.0 h
- Implementation2.0 h
- Testing4.0 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 $2,752.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-56156 — 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-2026-56156 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