CVE-2026-55016
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 · uneditedImproper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office SharePoint allows an authorized attacker to perform spoofing over a network.
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 confidenceThis is a cross-site scripting (XSS) vulnerability in Microsoft Office SharePoint where improper input neutralization allows an authenticated attacker to inject malicious scripts into web pages, potentially enabling session hijacking and spoofing attacks against other users.
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< 16.0.19725.20434= 2016= 2019CVSS 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
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
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 SharePoint versionOpen SharePoint Central Administration > System Settings > Manage servers in this farm. The version is displayed in the 'Configuration Database Version' column, or run Get-SPFarm | Select-Object BuildVersion in SharePoint Management ShellAffected if Installed version number is less than 16.0.19725.20434, or shows as SharePoint Server 2016 or SharePoint Server 2019 (any build)
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Confirm farm version matches 2016 or 2019In Central Administration > Help > About SharePoint Foundation, verify the exact version string. SharePoint 2016 typically shows version 16.x and SharePoint 2019 shows version 16.0.xAffected if Version string indicates SharePoint 2016 or SharePoint 2019 regardless of build number
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Check if SharePoint web applications are runningIn Central Administration > Application Management > Manage web applications, verify that web applications are provisioned and accessibleAffected if Web applications are provisioned and users can access SharePoint pages via browser
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Verify authentication is enabledConfirm thatForms-Based Authentication or Windows Authentication is configured in Central Administration > Authentication ProvidersAffected if Any form of user authentication is enabled allowing users to log in to SharePoint
Your SharePoint environment is affected if it is version 2016 or 2019 (any build), or any version lower than 16.0.19725.20434, and has web applications accessible to authenticated users where custom or user-supplied content can be entered.
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.
dbcve · scoped16.0.19725.20434
Implement proper input validation and output encoding for all user-supplied data in SharePoint pages; configure Content Security Policy (CSP) headers to restrict script execution; apply Microsoft security patches when available.
SharePoint Server 2016/2019 with build >= 16.0.19725.20434
- 1. Identify the current SharePoint Server version by checking the build number in SharePoint Central Administration > System Settings > Manage farm servers
- 2. For SharePoint Server 2016 and 2019, apply the Microsoft security update that addresses CVE-2026-55016, which will upgrade the build to version 16.0.19725.20434 or later
- 3. Verify the update was successfully applied by confirming the build number is now 16.0.19725.20434 or higher
- 4. Test critical SharePoint workflows and web parts to ensure functionality is preserved after the update
- 5. Clear browser caches and test for any residual XSS-related issues in custom web parts or third-party solutions
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-55016 — 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-2026-55016 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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