Advisory Details

July 19th, 2021

Microsoft SharePoint SetVariableActivity Deserialization of Untrusted Data Remote Code Execution Vulnerability

ZDI-21-828
ZDI-CAN-13358

CVE ID CVE-2021-34520
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/en-us/vulnerability/CVE-2021-34520
DISCLOSURE TIMELINE
  • 2021-03-26 - Vulnerability reported to vendor
  • 2021-07-19 - Coordinated public release of advisory
CREDIT Anonymous
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