Microsoft released ProxyLogon security updates for Microsoft Exchange servers running vulnerable unsupported Cumulative Update versions. The IT giant reported that at least one China-linked APT group, tracked as HAFNIUM, chained these vulnerabilities to access on-premises Exchange servers to access email accounts, and install backdoors to maintain access to victim environments. US Cybersecurity and Infrastructure Security Agency issued the Emergency Directive 21-02 in response to the disclosure of zero-day vulnerabilities in Microsoft Exchange. Microsofts move aims to temporarily protect the servers of its customers until they can install the latest updates for the Exchange servers.”]
Source: https://securityaffairs.co/wordpress/115428/security/microsoft-exchange-emergency-update.html