Microsoft on-premises zero-day vulnerabilities

  • CVE-2021–26857: CVSS 7.8: an insecure deserialization vulnerability in the Exchange Unified Messaging Service, allowing arbitrary code deployment under SYSTEM. However, this vulnerability needs to be combined with another or stolen credentials must be used.
  • Microsoft Exchange Server 2013
  • Implement an IIS Re-Write Rule to filter malicious https requests
  • Disable Unified Messaging (UM)
  • Disable Exchange Control Panel (ECP) VDir

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