EUVD-2026-56706
GHSA-8r25-8pqr-9xg6
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Network-delivered deserialization exploit requires only a valid SharePoint account (PR:L); no special conditions (AC:L); arbitrary code execution yields full C/I/A impact with unchanged scope.
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 allows any authenticated network attacker to execute arbitrary code by submitting a malicious serialized object payload to vulnerable endpoints. Three major SharePoint versions are affected - SharePoint Server 2016, 2019, and Subscription Edition - all running build versions below their respective patched thresholds. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a valid, authenticated SharePoint account with at minimum low-level user privileges - the CVSS PR:L metric and the description's 'authorized attacker' language both confirm this. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 score of 8.8 reflects genuine elevated risk: the network attack vector, low complexity, and absence of required user interaction mean exploitation is straightforward for any attacker holding a valid SharePoint credential. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with a low-privileged SharePoint user account - obtained through credential theft, phishing, or as a legitimate insider - crafts a malicious .NET serialized object payload targeting the vulnerable deserialization endpoint in SharePoint. The payload is submitted over the network via an HTTP/HTTPS request, and the SharePoint server deserializes the object without validation, executing the embedded gadget chain in the context of the SharePoint application pool service account. … |
| Remediation | Apply Microsoft's cumulative updates immediately: upgrade SharePoint Server 2019 to build 16.0.10417.20198 or later, SharePoint Server Subscription Edition to build 16.0.19725.20522 or later, and SharePoint Enterprise Server 2016 to build 16.0.5565.1001 or later. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, conduct an inventory of all SharePoint Server deployments across the organization (2016, 2019, and Subscription Edition instances), identify systems hosting business-critical content, and test the vendor-released patch in a pre-production environment to validate compatibility with custom solutions. …
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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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