Zero-day vulnerabilities in Microsoft Exchange Server

We are working on an accelerated timeline to release a fix

Microsoft is investigating two reported zero-day vulnerabilities affecting Microsoft Exchange Server 2013, Exchange Server 2016, and Exchange Server 2019. The first one, identified as CVE-2022-41040, is a Server-Side Request Forgery (SSRF) vulnerability, and the second one, identified as CVE-2022-41082, allows Remote Code Execution (RCE) when PowerShell is accessible to the attacker.

Currently, Microsoft is aware of limited targeted attacks using these two vulnerabilities.  In these attacks, CVE-2022-41040 can enable an authenticated attacker to remotely trigger CVE-2022-41082. It should be noted that authenticated access to the vulnerable Exchange Server is necessary to successfully exploit either vulnerability.

We are working on an accelerated timeline to release a fix. Until then, we’re providing mitigations and the detections guidance below to help customers protect themselves from these attacks.

Microsoft Exchange Online has detections and mitigations to protect customers. As always, Microsoft is monitoring these detections for malicious activity, and we’ll respond accordingly if necessary to protect customers.

Microsoft Security Threat Intelligence teams have provided further analysis of observed activity along with mitigation and detection guidance in a new Microsoft Security blog.


Exchange Online customers do not need to take any action.

The current Exchange Server mitigation is to add a blocking rule in “IIS Manager -> Default Web Site -> URL Rewrite -> Actions” to block the known attack patterns. Exchange Server customers should review and choose only one of the following three mitigation options.

Option 1: For customers who have the Exchange Emergency Mitigation Service (EEMS) enabled, Microsoft released the URL Rewrite mitigation for Exchange Server 2016 and Exchange Server 2019. The mitigation will be enabled automatically. Please see this blog post for more information on this service and how to check active mitigations.

Option 2: Microsoft created the following script for the URL Rewrite mitigation steps.

Option 3: Customers can follow the below instructions, which are currently being discussed publicly and are successful in breaking current attack chains.


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