CVE-2026-55139
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 allows an unauthorized attacker to disclose information 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 where the software reads memory beyond allocated buffer boundaries. This allows a local attacker to potentially access sensitive information from the application's memory space through a specially crafted file or input.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/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 run 'winword.exe /?' from Command Prompt to see the version number. Also check Windows Registry: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\ClickToRun\Configuration or HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\version\Common\InstallRootAffected if The installed version matches a version known to be affected by CVE-2026-55139 according to Microsoft's official security bulletin (compare your version to Microsoft's published affected version range)
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Verify if security updates are installedOpen Windows Update history (Settings > Update & Security > Windows Update > View update history) or check the installed updates list for recent Microsoft Office security patches. In Office apps, check File > Account > Update Options > View Update HistoryAffected if No recent Microsoft Office security updates are installed, leaving the out-of-bounds read vulnerability unpatched
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Assess file opening behaviorWhen opening documents from untrusted or unknown sources (especially .docx, .xlsx, .pptx, .docm, .xlsm files), observe if Office applications exhibit unusual behavior, crashes, or memory access patternsAffected if The user routinely opens Office documents from untrusted external sources without verification, creating the attack condition for this vulnerability
A user is affected if their installed Microsoft Office version falls within the affected range and lacks the corresponding security patch for CVE-2026-55139, combined with the realistic attack vector of opening a specially crafted Office document.
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 the latest Microsoft Office security updates to address this vulnerability. Since this is a local attack vector, ensure systems are kept current and consider restricting access to untrusted Office documents.
- Consultation1.0 h
- Implementation2.0 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 $1,664.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-55139 — 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-2026-55139 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