CVE-2026-35439
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 authorized 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 an authenticated attacker to deserialize untrusted data, leading to arbitrary code execution over the network.
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< 16.0.19725.20280= 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
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/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 versionRun Get-SPServer -Identity $env:COMPUTERNAME | Select-Object * in SharePoint Management Shell, or check Registry key HKLM\SOFTWARE\Microsoft\Shared Tools\Version\ProductVersion, or access SharePoint Central Administration > System Settings > Manage servers in this farmAffected if Version is lower than 16.0.19725.20280, or version matches 2016 or 2019
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Confirm SharePoint edition is Server (not Foundation or Online)Run Get-SPProduct -Local in SharePoint Management Shell and check the Product Name column shows 'SharePoint Server'Affected if The product is Microsoft SharePoint Server 2016 or 2019 (any build), or the installed Server version is below 16.0.19725.20280
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Verify external authentication methods are configuredCheck SharePoint Central Administration > Application Management > Manage web applications > Authentication Providers to see if any non-NTLM/Kerberos providers (Claims-based, Forms, etc.) are enabled, or run Get-SPTrustedAuthenticationProviderAffected if Any form of external or claims-based authentication is enabled, allowing authenticated attackers to interact with the deserialization endpoint
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Confirm the web application is accessible over networkVerify SharePoint web applications are listening on ports (typically 80, 443, or custom ports) via netstat -an | findstr LISTENING or by attempting to access the SharePoint site URLAffected if SharePoint is reachable over the network, enabling remote authenticated attackers to send malicious deserialized data
If the SharePoint Server version is 2016 or 2019, or is below 16.0.19725.20280, and the server is network-accessible with authentication enabled, the environment is likely affected by this deserialization 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.
From vendor data16.0.19725.20280
Apply Microsoft security patches for SharePoint as soon as they become available; in the meantime, restrict network access to SharePoint servers to authorized personnel only and monitor for anomalous deserialization activity.
- 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-2026-35439 — 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-2026-35439 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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