Advisory Details

October 21st, 2021

Microsoft SharePoint SetVariableActivity Deserialization of Untrusted Data Remote Code Execution Vulnerability

CVE ID	CVE-2021-40487
CVSS SCORE	8.8, AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
AFFECTED VENDORS	Microsoft
AFFECTED PRODUCTS	SharePoint
VULNERABILITY DETAILS	This vulnerability allows remote attackers to execute arbitrary code on affected installations of Microsoft SharePoint. Authentication is required to exploit this vulnerability. The specific flaw exists within the Microsoft.SharePoint.WorkflowActions.SetVariableActivity class. A crafted SetVariableActivity element can result in instantiation of an arbitrary .NET type. An attacker can leverage this vulnerability to execute code in the context of the web service account.
ADDITIONAL DETAILS	Microsoft has issued an update to correct this vulnerability. More details can be found at: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40487
DISCLOSURE TIMELINE	2021-08-25 - Vulnerability reported to vendor 2021-10-21 - Coordinated public release of advisory
CREDIT	Anonymous

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