The Exchange Server flaw is one of 55 vulnerabilities fixed in Microsoft's Patch Tuesday update.
An emerging threat called Tortilla has been exploiting vulnerabilities in Microsoft (MS) Exchange servers hit with Babuk ransomware.
New data from Microsoft shows that Nobelium, Thallium, and other nation-state attack groups are increasingly focusing on government agencies and NGOs.
Microsoft said that the threat group has used phishing and password-spraying attacks to compromise at least 14 IT service providers this year.
Microsoft issued a fix for a use-after-free Windows vulnerability that was being leveraged in attacks, as part of its October Patch Tuesday roundup.