SRC-2020-0027 : Microsoft Exchange Server NewExchangeCertificate WriteRequest File Overwrite Denial of Service Vulnerability



CVSS Score:

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

Affected Vendors:


Affected Products:

Exchange Server

Vulnerability Details:

This vulnerability allows remote attackers to cause a denial of service against affected installations of Exchange Server. Authentication with the “Exchange Server Certificates” role is required to exploit this vulnerability.

The specific flaw exists within the processing of the New-ExchangeCertificate cmdlet. The issue results from the lack of proper validation of user-supplied data when writing files. An attacker can leverage this vulnerability to cause a denial of service.

Vendor Response:

Microsoft has issued an update to correct this vulnerability. More details can be found at:

Disclosure Timeline:

  • 2020-05-18 – Sent to Microsoft
  • 2020-11-10 – Coordinated public release of advisory


This vulnerability was discovered by Steven Seeley (mr_me) of Qihoo 360 Vulcan Team