EUVD-2026-56295
GHSA-vcv9-wr6m-p5qc
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Network-reachable deserialization requiring only a low-privilege account; no user interaction; full CIA impact on the vulnerable server.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
3DescriptionCVE.org
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
AnalysisAI
Remote code execution in Microsoft SharePoint Server affects authenticated network users through unsafe deserialization of attacker-controlled data. Affected versions span SharePoint Server 2019, SharePoint Enterprise Server 2016, and SharePoint Server Subscription Edition - all running build numbers below the patched releases issued by Microsoft. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a valid, low-privilege SharePoint user account - the CVSS vector PR:L confirms that some level of authentication is necessary and unauthenticated exploitation is not possible. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) accurately reflects a serious, network-reachable, low-complexity vulnerability requiring only authenticated (low-privilege) access - meaning any SharePoint user account is sufficient to attempt exploitation. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with a valid low-privilege SharePoint user account (e.g., a compromised employee credential or a guest account) crafts a malicious serialized .NET object and submits it to a vulnerable SharePoint endpoint over the network. The server deserializes the payload without adequate validation, executing an attacker-controlled gadget chain that runs arbitrary code in the context of the SharePoint application pool. … |
| Remediation | Apply the Microsoft-released patches immediately: upgrade SharePoint Server 2019 to build 16.0.10417.20198 or later, SharePoint Enterprise Server 2016 to build 16.0.5565.1001 or later, and SharePoint Server Subscription Edition to build 16.0.19725.20522 or later. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, conduct a complete inventory of all Microsoft SharePoint Server 2019, 2016, and Subscription Edition deployments and immediately apply the vendor-released security patch from Microsoft to all instances, verifying successful deployment through change tracking. …
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Same weakness CWE-502 – Deserialization of Untrusted Data
View allSame technique Deserialization
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External POC / Exploit Code
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