Threat actors scan Internet for Vulnerable Microsoft Exchange Servers

Pierluigi Paganini February 27, 2020

Experts warn that hackers are actively scanning the Internet for Microsoft Exchange Servers vulnerable in the attempt to exploit the CVE-2020-0688 RCE.

Hackers are actively scanning the Internet for Microsoft Exchange Servers affected by the CVE-2020-0688 remote code execution flaw.

The vulnerability resides in the Exchange Control Panel (ECP) component, the root cause of the problem is that Exchange servers fail to properly create unique keys at install time.

“Knowledge of a the validation key allows an authenticated user with a mailbox to pass arbitrary objects to be deserialized by the web application, which runs as SYSTEM.” reads the advisory published by Microsoft.

A remote, authenticated attacker could exploit the CVE-2020-0688 vulnerability to execute arbitrary code with SYSTEM privileges on a server and take full control.

Security experts Simon Zuckerbraun from Zero Day Initiative published technical details on how to exploit the Microsoft Exchange CVE-2020-0688 along with a video PoC.

“Similarly, any outside attacker who compromised the device or credentials of any enterprise user would be able to proceed to take over the Exchange server. Having accomplished this, an attacker would be positioned to divulge or falsify corporate email communications at will.” wrote Zuckerbraun. “Accordingly, if you’re an Exchange Server administrator, you should treat this as a Critical-rated patch and deploy it as soon as your testing is complete. Microsoft lists this with an Exploit Index of 1, which means they expect to see exploits within 30 days of the patch release.”

Now the popular security researcher Kevin Beaumont reported mass scanning for the CVE-2020-0688 (Microsoft Exchange 2007+ RCE vulnerability).

Attackers, in order to exploit the issue, have to find a vulnerable server exposed online, search for email addresses they collect from the Outlook Web Access (OWA) portal URL, and use data from previous data breaches to launch a credential stuffing attack.

“Next, they only have to launch a credential stuffing attack and keep at it until they get a hit and are able to login to the server. Once in, all that’s left is to exploit the CVE-2020-0688 vulnerability and fully compromise the targeted Exchange server.” reported BleepingComputer.

Beaumont explained that the process could be automated by using open tools available online, and these tools are currently actively used by threat actors in the wild.

Experts urge administrators to patch their servers before attackers could reach them and exploit the CVE-2020-0688 flaw.

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Pierluigi Paganini

(SecurityAffairs – Microsoft Exchange, CVE-2020-0688)

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