Advisory Details

July 22nd, 2021

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

ZDI-21-894
ZDI-CAN-13610

CVE ID CVE-2021-31198
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 OAB service. The issue results from the lack of proper validation of user-supplied data, which can allow arbitrary files write to OAB folders. 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-2021-31198
DISCLOSURE TIMELINE
  • 2021-04-07 - Vulnerability reported to vendor
  • 2021-07-22 - Coordinated public release of advisory
CREDIT rskvp93 of Team Viettel - Viettel Cyber Security
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