EUVD-2026-56428
GHSA-cqmq-63vg-9mc5
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Network-delivered deserialization requiring only a valid user account (PR:L); no user interaction; full system impact with scope unchanged to SharePoint host.
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 exposes organizations to full system compromise via deserialization of attacker-controlled data submitted over the network. Versions across three SharePoint Server editions (Subscription Edition, 2019, and Enterprise 2016) are confirmed affected, all requiring only a low-privileged authenticated account to exploit. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The attacker must possess a valid SharePoint user account with at minimum low-level access permissions (PR:L per CVSS vector); unauthenticated exploitation is not indicated by the available data. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS score of 8.8 reflects a genuinely high-risk posture: network-accessible (AV:N), low complexity (AC:L), no user interaction (UI:N), and full confidentiality, integrity, and availability impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker holding a low-privileged SharePoint user account - such as a malicious insider or an external attacker who has compromised any user's credentials - constructs a serialized .NET object payload containing a known gadget chain and submits it to the SharePoint server via a standard network request. The SharePoint server processes the serialized data without sufficient validation, triggering arbitrary code execution in the context of the SharePoint service account. … |
| Remediation | The primary remediation is to apply Microsoft's released security update immediately. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all Microsoft SharePoint Server deployments to identify which systems run Subscription Edition, 2019, or Enterprise 2016, and enumerate the internal user populations with authenticated access to these instances. …
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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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