CVE-2026-20963
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 · uneditedDeserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.
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 deserialization vulnerability in Microsoft Office SharePoint allows unauthenticated remote attackers to execute arbitrary code by sending specially crafted serialized data to affected SharePoint installations. The critical CVSS score of 9.8 indicates this is a readily exploitable vulnerability that can be weaponized for complete system compromise without authentication.
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< 16.0.19127.20442= 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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 SharePoint Server versionUse SharePoint Central Administration > System Settings > Manage farm servers, or run PowerShell: Get-SPFarm | Select-Object BuildVersion. Also check registry key: HKLM\SOFTWARE\Microsoft\Shared Tools\Web Server Extensions\16.0\SharePoint\Setup\VersionAffected if Version is below 16.0.19127.20442, or the build matches SharePoint Server 2016 or 2019
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Confirm SharePoint editionCheck product information in Central Administration or run: (Get-SPFarm).Products to list installed SharePoint productsAffected if SharePoint Server 2016 or SharePoint Server 2019 is installed regardless of patch level
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Verify SharePoint Web Services are network-accessibleTest HTTP/HTTPS access to SharePoint sites from external locations using curl or Invoke-WebRequest: curl -I https://your-sharepoint-siteAffected if SharePoint is exposed to untrusted networks without authentication restrictions
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Inspect SharePoint farm configuration for deserialization endpointsReview SharePoint web.config files in IIS for ViewState or other deserialization handlers, and check ULS logs for .NET BinaryFormatter/LosFormatter activityAffected if Deserialization handlers are accessible to unauthenticated users
You are affected if your SharePoint Server is version 16.0.19127.20442 or lower, or is specifically the 2016 or 2019 edition, AND is network-accessible to unauthenticated attackers.
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 · scoped16.0.19127.20442
Apply Microsoft security updates for SharePoint immediately when available. Until patches are deployed, consider network segmentation to limit SharePoint exposure and implement Web Application Firewall rules to detect deserialization attack patterns.
SharePoint Server 2016/2019 to version 16.0.19127.20442 or later
- Identify the current SharePoint Server version installed in your environment
- Review Microsoft Update Catalog or SharePoint Server release notes for version 16.0.19127.20442 or later
- Plan upgrade during a maintenance window to minimize business impact
- Apply the update following Microsoft documentation for your SharePoint version (2016 or 2019)
- Verify the update was successful by checking the SharePoint version under Central Administration > System Settings > Manage servers in this farm
- Test critical SharePoint functionality post-update
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,968.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20963 — 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-2026-20963 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