CVE-2026-42831
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 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 heap-based buffer overflow vulnerability in Microsoft Office enables an unauthenticated attacker to achieve local code execution. The vulnerability stems from improper bounds checking when processing specially crafted Office documents, allowing heap memory corruption and arbitrary code execution in the context of the current user.
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 data< 16.0.19822.20190= 2024= 2021CVSS 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 Microsoft Office versionOpen any Office application (Word, Excel, PowerPoint), go to File > Account > About [App], or check WINWORD.EXE properties in Program Files. For Microsoft 365, also check via File > Account > View Updates.Affected if Version is 2024 (any build), LTSC 2021 (any build), or Microsoft 365 Copilot version is below 16.0.19822.20190
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Confirm Office executable versionNavigate to the Office installation directory (typically C:\Program Files\Microsoft Office\root\Office16 or similar) and check properties of WINWORD.EXE, EXCEL.EXE, or POWERPNT.EXE to view the File Version.Affected if The file version matches an affected release year (2024 or 2021) or falls below 16.0.19822.20190 for Microsoft 365 Copilot installations
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Check Microsoft 365 subscription version specificallyOpen any Microsoft 365 app, go to File > Account, and note the version number displayed under 'Update Options' or 'About [App]'. Compare the full version string (e.g., 16.0.xxxxx.xxxxx) to the threshold.Affected if The version number is less than 16.0.19822.20190 and the product includes Copilot functionality
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Determine vulnerability applicability based on document processingThe flaw triggers when Office processes specially crafted documents. Verify if the system regularly opens Office files from email attachments, downloads, or network shares - this is the attack surface.Affected if An affected Office version is installed AND the user or application opens Office documents (DOCX, XLSX, PPTX, etc.) from any source
A user is affected if their installed Microsoft Office version is 2024, LTSC 2021, or Microsoft 365 Copilot below version 16.0.19822.20190, and they process Office documents.
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 data16.0.19822.20190
Apply available Microsoft Office security updates promptly. Until patches are deployed, exercise caution with Office documents from untrusted sources and consider deploying enhanced monitoring for suspicious Office file activity.
- Consultation2.0 h
- Implementation1.0 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-2026-42831 — 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-2026-42831 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
- No spam, self-promotion, credentials, or personal data