CVE-2026-55031
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 · uneditedOut-of-bounds read 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 confidenceAn out-of-bounds read vulnerability exists in Microsoft Office Excel where the software reads memory beyond allocated buffer boundaries. This memory corruption can be leveraged by an attacker to achieve local code execution, likely through a specially crafted Excel file that triggers the improper memory access when opened by a victim.
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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Identify installed Excel versionOpen Excel, go to File > Account > About Excel, or run 'excel.exe /?' from Command Prompt to view version informationAffected if Version shows as Microsoft Excel 2016, 2019, 2021, 2024, or part of Microsoft 365 Apps (all versions listed are affected)
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Check Office version via registryRun 'reg query "HKLM\Software\Microsoft\Office\ClickToRun\Configuration" /v VersionToReport' or check HKLM\Software\Microsoft\Office\{version}\Excel\InstallRoot for version stringsAffected if Any version string returned indicates an affected Office installation
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Verify Excel component file versionLocate excel.exe (typically in C:\Program Files\Microsoft Office\root\OfficeXX or C:\Program Files (x86)\Microsoft Office\root\OfficeXX), right-click > Properties > Details to see File VersionAffected if File version is present and matches any of the affected Office versions (2016 through 2024, or Microsoft 365)
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Check Office Online Server version (if applicable)If running Office Online Server, run PowerShell 'Get-OfficeWebAppsServer' or check the file version of wacserver.exe or relevant wac farm DLLsAffected if Office Online Server version is below 16.0.10417.20175
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Confirm Excel is the affected componentThis vulnerability specifically affects Excel. Verify Excel is installed by checking for excel.exe or via Office installation statusAffected if Excel is installed (the vulnerability exists in Excel component of any affected Office/365 version)
If any version of Excel from Office 2016, 2019, 2021, 2024, Microsoft 365 Apps, or Office Online Server below build 16.0.10417.20175 is installed, the environment is affected by this out-of-bounds read vulnerability.
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 security updates for Excel as they become available through standard patch management processes. Organizations should ensure Microsoft Office is kept current and consider using Protected View or application sandboxing for untrusted Excel files.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-55031 — 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-2026-55031 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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