Risk Letters

Exploited vulnerability

CVE-2021-26858

TLP:CLEAR

Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.

Facts

  • Vendor: Microsoft
  • Product: Exchange Server
  • CVSS: 7.8
  • EPSS (probability of exploitation within 30 days): 93.7 %
  • On CISA's Known Exploited Vulnerabilities list since: 3 November 2021
  • First known exploitation: 3 November 2021
  • Used in ransomware campaigns (per CISA): Yes
  • CISA's deadline for US federal agencies: 3 May 2022
  • First seen by Risk Letters: 3 November 2021

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Data: NVD (public domain), CISA KEV, FIRST EPSS, MITRE ATT&CK, AlienVault OTX. NVD