Microsoft Exchange PowerShell Unsafe Reflection NTLM Relay Vulnerability

October 16th, 2024
ZDI-23-003 ZDI-CAN-19042

CVE ID

CVE-2023-21745

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 relay NTLM credentials on affected installations of Microsoft Exchange. Authentication is required to exploit this vulnerability.

The specific flaw exists within the PowerShell endpoint. The process does not properly restrict a user-supplied argument before using it to create an instance of an object. An attacker can leverage this vulnerability to relay NTLM credentials 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/vulnerability/CVE-2023-21745

Disclosure Timeline

  • 2022-09-29 - Vulnerability reported to vendor
  • 2024-10-16 - Coordinated public release of advisory
  • 2024-10-16 - Advisory Updated

Credit

Piotr Bazydlo (@chudypb) of Trend Micro Zero Day Initiative

Back to Advisories