Zero-day Microsoft exchange vulnerabilities attack IOC
by CIRT Team
Microsoft has detected multiple 0-day exploits being used to attack on-premises versions of Microsoft Exchange Server in limited and targeted attacks. In the attacks observed, the threat actor used these vulnerabilities to access on-premises Exchange servers which enabled access to email accounts, and allowed installation of additional malware to facilitate long-term access to victim environments.
The vulnerabilities recently being exploited were CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-27065.
CVE-2021-26855 is a server-side request forgery (SSRF) vulnerability in Exchange which allowed the attacker to send arbitrary HTTP requests and authenticate as the Exchange server.
CVE-2021-26857 is an insecure deserialization vulnerability in the Unified Messaging service.
CVE-2021-26858 is a post-authentication arbitrary file write vulnerability in Exchange.
CVE-2021-27065 is a post-authentication arbitrary file write vulnerability in Exchange.
Indicator of compromise (IoC) in computer forensics is an artifact observed on a network or in an operating system that, with high confidence, indicates a computer intrusion.
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|188.8.131.52 184.108.40.206 220.127.116.11 18.104.22.168 22.214.171.124 126.96.36.199 188.8.131.52 184.108.40.206 220.127.116.11 18.104.22.168 22.214.171.124 126.96.36.199 188.8.131.52 184.108.40.206 220.127.116.11 18.104.22.168 22.214.171.124
Successful response should consist of the following steps:
- Deploy updates to affected Exchange Servers.
- Investigate for exploitation or indicators of persistence.
- Remediate any identified exploitation or persistence and investigate your environment for indicators of lateral movement or further compromise.
- Investigate for exploitation, persistence, or evidence of lateral movement
- Analyze the Exchange product logs for evidence of exploitation.
- Scan for known web shells.
- Use the updated IOC feed for newly observed indicators.
- Leverage other organizational security capabilities
For more information and Recommendation please visit following reference URL’s: