Microsoft Exchange Server ECP Authentication Bypass Information Disclosure Vulnerability

July 15th, 2021
ZDI-21-798 ZDI-CAN-13477

CVE ID

CVE-2021-33766

CVSS Score

6.5 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

Affected Vendors

Microsoft

Affected Products

Exchange

Vulnerability Details

This vulnerability allows remote attackers to disclose sensitive information on affected installations of Microsoft Exchange Server. Authentication is not required to exploit this vulnerability.

The specific flaw exists within the authentication of requests to web services within the ecp web application. By issuing a crafted request, an attacker can bypass authentication. An attacker can leverage this vulnerability to disclose information from the server.

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-2021-33766

Disclosure Timeline

  • 2021-04-05 - Vulnerability reported to vendor
  • 2021-07-15 - Coordinated public release of advisory

Credit

LE XUAN TUYEN - VNPT ISC

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