Microsoft Releases Mitigation Tool for On-Premises Exchange Servers

Microsoft has released a mitigation tool to help organizations that lack IT and security support as they work to patch their Microsoft Exchange Servers and defend against ongoing attacks.

The new one-click Microsoft Exchange On-Premises Mitigation Tool is meant to serve as an interim mitigation for those that aren't familiar with the patching process or that haven't yet applied the Exchange security updates released on March 2, Microsoft explains in a blog post. The company last reported some 82,000 Exchange Servers remain vulnerable to the exploits.

This is not a replacement for the Exchange Server security update, Microsoft says, but it is an efficient way to defend against the highest risks to Internet-connected, on-premises Exchange Servers for organizations that haven't yet applied the patch. The tool has been tested across Exchange Server 2013, 2016, and 2019, all of which are affected by the recently patched flaws. 

Organizations that haven't updated their systems are advised to download and run the tool on their Exchange Servers. This will automatically mitigate CVE-2021-26855 with a URL rewrite configuration, run a malware scan, and reverse changes made by identified threats, Microsoft says.

While the tool is effective against attacks seen so far, officials warn it's not guaranteed to protect against potential future attack techniques. Organizations are still urged to fully update their systems as soon as possible. 

Read more information about the tool here.