ProxyToken (CVE-2021-33766): Authentication Bypass in Microsoft Exchange Server

UPDATE 9/17 - An IPS signature has been released in definitions (18.160) as "MS.Exchange.Server.SecurityToken.Authentication.Bypass"FortiGuard Labs is aware of a new disclosure dubbed PROXYTOKEN, which is an authentication bypass in Microsoft Exchange server. The vulnerability was reported by security researcher Le Xuan Tuyen of the Zero Day Initiative (ZDI) in March 2021, and patched by Microsoft in the July 2021 release.Assigned CVE-2021-33766, this vulnerability allows an unauthenticated attacker to configure actions on mailboxes belonging to arbitrary users on the mail server. …

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