(Pwn2Own) Microsoft Exchange Server Arbitrary File Write Remote Code Execution Vulnerability

July 19th, 2021
ZDI-21-819 ZDI-CAN-13588

CVE ID

CVE-2021-31207

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

Exchange

Vulnerability Details

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Microsoft Exchange Server. Although authentication is required to exploit this vulnerability, the existing authentication mechanism can be bypassed.

The specific flaw exists within the handling of mailbox export. The issue results from the lack of proper validation of user-supplied data, which can allow the upload of arbitrary files. An attacker can leverage this vulnerability to execute arbitrary code in the context of SYSTEM.

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-2021-31207

Disclosure Timeline

  • 2021-07-16 - Vulnerability reported to vendor
  • 2021-07-19 - Coordinated public release of advisory

Credit

Orange Tsai(@orange_8361) from DEVCORE Research Team

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