Microsoft has released an alert urging organisations to apply the recently released patch for Microsoft Exchange Server as soon as possible, detecting multiple Zero-day exploits being actively targeted in the wild. The observed attacks have been attributed to a Chinese state-sponsored threat actor, targeting Exchange vulnerabilities to gain access to multiple victim networks and exfiltrate data.
The exploited vulnerabilities are CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-27065 which have all been addressed in Microsoft’s patch release early this week.
We recommend applying these security updates to all vulnerable systems as soon as possible, prioritising those that are internet-facing. If the patches can not be applied immediately, consider taking additional steps to prevent successful exploitation.
The Equate Managed Security Team responded instantly to this Microsoft alert using a five-stage approach: