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CVE-2018-8421 is a critical remote code execution vulnerability in Microsoft .NET Framework’s workflow processing, specifically involving compilation and handling of untrusted XOML workflow input in the System.Workflow stack. According to the provided content, the issue is a deserialization flaw that allows attackers to bypass workflow protection mechanisms enforced by the Windows Workflow Compiler, including the /nocode and /checktypes options. These protections are intended to prevent code-behind execution and restrict workflows to approved types, but crafted XOML content can still trigger unsafe deserialization and gadget invocation. Research cited in the content demonstrated multiple proof-of-concept gadget chains, including ObjectDataProvider, WorkflowDesigner, and later ProcessStartInfo/ObjectInstance-based approaches, showing that attacker-controlled workflow definitions could lead to command execution during workflow compilation or processing. SharePoint was identified as a practical exploitation target because authenticated users could create workflows, but the issue was broader than SharePoint and affected other applications that compile XOML files on vulnerable .NET Framework versions.
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A .NET Framework deserialization vulnerability tied to remote code execution in SharePoint Workflows, affecting SharePoint Online and on-premises versions.
A critical .NET Framework Workflow/XOML deserialization issue that bypasses /nocode and /checktypes protections and can lead to remote code execution, including on SharePoint servers via workflow compilation/validation.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
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