![]() ![]() ![]() The Frontend Proxy first makes use of the “GetTargetBackendServerURL” method to determine which Backend URL the HTTP request should be forwarded to. The implementation code of the Exchange server consists of a method called “GetTargetBackEndServerUrl” which retrieves the Backend URL from the static resource handler and it directly assigns the Backend target with the use of cookies. OWA runs on port 443 whereas Exchange Backend service is bound to port 444.Įxhibit: This is where the ProxyLogon vulnerability exists (source: BlackHat Conference) Instead, they have to go via frontend APIs like Outlook Web Apps (OWA).Ī proxy lies between the client and the backend service in order to transfer requests between OWA and the backend. Clients cannot directly communicate with backend services. Each server runs multiple layers of protocols that are used for enabling access to the various clients and to communicate with the servers. Microsoft Exchange server has an architecture consisting of multiple building blocks designed for providing availability, load balancing, and communication between different servers. ![]() CVE-2021-26855 is a bug that results in authentication bypass by performing pre-authentication SSRF.ĬVSS Vector - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H WHERE IS THE VULNERABILITY PRESENT? ![]() Discovered in 2021, this vulnerability allows anyone, without any prior authentication, to easily execute the exploit code on Microsoft Exchange Server through port 443. Microsoft Exchange ServerSide Request Forgery (SSRF), popularly known as ProxyLogon, is the most well known Microsoft Exchange Server vulnerability. ![]()
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