CVE-2026-55135
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 confidenceCross-site scripting (XSS) vulnerability in Microsoft Office SharePoint allows an authenticated attacker to inject malicious scripts through improper input neutralization, enabling spoofing attacks via the web interface.
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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Check SharePoint Server version via PowerShellOpen SharePoint Management Shell and run: (Get-SPFarm).BuildVersion.ToString() or Get-SPServer | Select-Object -Property Name, BuildVersionAffected if The version returned is below 16.0.19725.20434, or equals 16.0.5435.1000 (SharePoint 2016), or equals 16.0.10388.20001 (SharePoint 2019)
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Verify SharePoint edition is ServerIn SharePoint Management Shell run: Get-SPFarm | Select-Object -Property ProductsAffected if The output includes 'Microsoft SharePoint Server' (not Foundation or Online) and the version check above shows an affected version
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Confirm Central Administration is accessible via webAccess Central Administration site (typically port 2019 or 2016) in a browser and verify login worksAffected if The web interface is accessible and the server version is in the affected range - the XSS could be triggered through web requests to SharePoint pages
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Identify any custom web parts or formsReview customizations in SharePoint Designer or check _layouts/15/pages for custom .aspx pages in the web applicationAffected if Custom web parts exist that accept user input and render it without encoding; combined with affected version, these could be exploitation vectors
A SharePoint Server 2016 or 2019 installation, or any version prior to 16.0.19725.20434, with an authenticated user able to access the web interface is potentially affected by this XSS 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.
dbcve · scoped16.0.19725.20434
Implement proper output encoding and input validation for all user-supplied data in SharePoint pages and web parts; apply security updates when released by Microsoft.
SharePoint Server 2016 or 2019 with build 16.0.19725.20434 or later (latest supported cumulative update)
- Check your current SharePoint Server build version via Central Administration > System Settings > Manage servers in this farm
- Navigate to Microsoft Update Catalog or your Microsoft 365 admin center to obtain the latest security update for your SharePoint version
- For SharePoint Server 2016: Install the latest security update from Microsoft Update (typically released as a CU)
- For SharePoint Server 2019: Install the latest security update from Microsoft Update (typically released as a CU)
- After installation, run the SharePoint Products Configuration Wizard on all servers in the farm
- Verify the build number has been updated to 16.0.19725.20434 or later
- Test critical SharePoint workflows to confirm functionality
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA8.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $12,352.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-55135 — 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-2026-55135 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