SRC-2020-0031 : Microsoft Exchange Server EWS RouteComplaint ParseComplaintData XML External Entity Processing Information Disclosure Vulnerability

CVE ID: CVE-2020-17141

CVSS Score: 8.8, (/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C)

Affected Vendors: Microsoft

Affected Products: Microsoft Exchange Server

Vulnerability Details:

This vulnerability allows remote attackers to disclose information on affected installations of Exchange Server. Authentication is required to exploit this vulnerability.

The specific flaw exists within the processing of RouteComplaint SOAP requests to the EWS service endpoint. The issue results from the lack of proper validation of a user-supplied xml. An attacker can leverage this vulnerability to disclose information in the context of SYSTEM.

Vendor Response:

Microsoft has issued an update to correct this vulnerability. More details can be found at: https://portal.msrc.microsoft.com/security-guidance/advisory/CVE-2020-17141

Disclosure Timeline:

  • 2020-04-23 – Sent to Microsoft

  • 2020-12-08 – Coordinated public release of advisory

Proof of Concept:

Credit: This vulnerability was discovered by Steven Seeley (mr_me) of Qihoo 360 Vulcan Team and Chris Anastasio