SRC-2020-0024 : Microsoft SharePoint Server TOCTOU ControlParameter Binding Remote Code Execution Vulnerability

CVE ID: CVE-2020-16951

CVSS Score: 8.6, (/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L/E:P/RL:O/RC:C)

Affected Vendors: Microsoft

Affected Products: SharePoint Server

Vulnerability Details:

This vulnerability allows remote attackers to execute arbitrary code on affected installations of SharePoint Server. Authentication is required to exploit this vulnerability.

The specific flaw exists within the WebPartEditingSurfacePage class. The issue results from the lack of proper validation of user-supplied control markup. An attacker can leverage this vulnerability to execute code in the context of the local Administrator.

Vendor Response:

Microsoft has issued an update to correct this vulnerability. More details can be found at: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2020-16951

Disclosure Timeline:

• 2020-08-13 – Sent to Microsoft
• 2020-11-10 – Coordinated public release of advisory

Proof of Concept:

• /pocs/cve-2020-16951.py.txt

Credit: This vulnerability was discovered by Steven Seeley (mr_me) of Qihoo 360 Vulcan Team and Yuhao Weng (@cjm00nw)