CVE-2026-40365
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 confidenceThis is a deserialization vulnerability in Microsoft Office SharePoint where an authenticated attacker can deserialize untrusted data, leading to remote code execution. The attack can be carried out over the network, indicating the vulnerability is remotely exploitable.
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 SharePoint Server versionOpen SharePoint Central Administration > System Settings > Manage farm servers OR run Get-SPFarm | Select-Object BuildVersion in SharePoint Management ShellAffected if Version is less than 16.0.19725.20280 OR version equals 2016 OR version equals 2019
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Confirm SharePoint editionIn Central Administration > Farm Management > Farm Configuration > Configure Product and Farm Configuration Wizard, verify the edition is SharePoint Server (not Foundation)Affected if Product is Microsoft SharePoint Server and version matches affected ranges from step 1
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Check SharePoint web application authenticationIn Central Administration > Web Applications > Manage Web Applications, verify if any web applications are using classic mode authentication or forms-based authentication that accept deserialized dataAffected if Web applications exist and are accessible over network with authenticated user access enabled
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Verify deserialization features are in useReview SharePoint farm solutions and any custom web parts that handle serialized data objects. Check ULS logs for BinaryFormatter or LosFormatter usage patterns if availableAffected if Custom solutions or third-party extensions that handle serialized objects are deployed on the farm
The environment is affected if SharePoint Server version is 2016, 2019, or any version below 16.0.19725.20280, and the server accepts authenticated user connections over the network.
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 · scoped16.0.19725.20280
Apply the latest Microsoft SharePoint security updates as soon as possible. Review and restrict SharePoint permissions to minimize the attack surface for authorized users.
SharePoint Server 2016 or 2019 with security update to version 16.0.19725.20280 or later
- 1. Review the Microsoft Security Response Center (MSRC) bulletin for CVE-2026-40365 to obtain the specific security update KB number
- 2. Download and apply the relevant security update for your SharePoint Server version (2016 or 2019) from the Microsoft Update Catalog or through your WSUS server
- 3. After applying the update, verify the SharePoint Server services are running correctly
- 4. Test critical SharePoint workflows to ensure functionality is not impacted
- 5. Document the update applied for compliance and audit purposes
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation6.0 h
- Implementation12.0 h
- Testing10.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,928.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-40365 — 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-2026-40365 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