EUVD-2026-56750
GHSA-3hq7-6h7j-3wxc
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Network-exploitable deserialization requiring only low-privilege authenticated access; no user interaction; full confidentiality, integrity, and availability impact on the vulnerable system.
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 Office SharePoint exploits unsafe deserialization of attacker-controlled data over the network. An authenticated attacker with low-level network access can submit a crafted serialized payload that SharePoint deserializes without sufficient validation, resulting in full compromise of confidentiality, integrity, and availability. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the attacker hold a valid, authenticated account on the target SharePoint instance with at minimum low-privilege access (PR:L per CVSS vector). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS base score of 8.8 with vector AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H reflects a high-severity, network-exploitable flaw requiring only low-privilege credentials and no user interaction. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with a valid low-privilege SharePoint account - such as a standard domain user in an organization with broad SharePoint access - crafts a malicious serialized .NET object and submits it to a vulnerable SharePoint endpoint over the network. SharePoint deserializes the payload without adequate validation, triggering a gadget chain that executes arbitrary code in the context of the SharePoint application pool. … |
| Remediation | The primary remediation is to apply the vendor-released patch via Microsoft's Security Update Guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66808. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, audit your Microsoft Office SharePoint infrastructure to identify affected systems and assess exposure to less-trusted network segments or external access; document systems containing sensitive data for prioritization. …
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Same weakness CWE-502 – Deserialization of Untrusted Data
View allSame technique Deserialization
View allVendor StatusVendor
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External POC / Exploit Code
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