Microsoft Release Multiple Security Updates for Exchange Server after Zero-day Exploitation

Mar/04/2021

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:

Identifying vulnerable systems in customer networks;
Providing advice and remediation recommendations based on threat intelligence;
Pro-actively blocking and searching available Indicators of Compromise (IOC’s);
Applying technical mitigations to prevent successful exploitation of the vulnerability;
Ongoing management and 24 x 7 monitoring of networks and systems.

Click here for IOCs taken from the observed attacks in the wild
Microsoft’s advice on the security updates can be found here.

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Microsoft Release Multiple Security Updates for Exchange Server after Zero-day Exploitation

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