Hazard

Is CVE-2021-27065 being exploited?

Ransomware crews are using this

CISA has linked this vulnerability to known ransomware campaigns. Treat any exposed instance as an active incident, not a patching ticket.

Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft · Exchange Server

CVSS 7.8 EPSS 100% 1 public exploit ransomware Fix deadline passed 3 May 2022

What it is

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

Why we say that

  • Linked by CISA to known ransomware campaigns
  • EPSS puts exploitation in the next 30 days at 100%
  • 1 public exploit published
  • CISA's federal remediation deadline (2022-05-03) has passed
  • Listed in the CISA Known Exploited Vulnerabilities catalogue

Every line above comes from a named public source. Where the evidence is thin, we say so rather than inventing confidence — see methodology.

What to do

Apply updates per vendor instructions.

Public exploit code

Indexed from Exploit-DB. Presence of code raises urgency; absence does not mean safety.

What it costs when this goes wrong

This is where UK enforcement meets the vulnerability record. This vulnerability is used in ransomware campaigns; here is what ransomware has cost UK organisations at the regulator.

All UK cases caused by ransomware →