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CVE-2021-42321

Microsoft Exchange Server Remote Code Execution Vulnerability

Actively exploited: CISA added it to its Known Exploited Vulnerabilities catalog on 17 Nov 2021.

Severity
High 8.8
Published
10 Nov 2021
Last changed
19 Aug 2026
Added to UpHeron
1 Nov 2026
Sources
NVD

Affected software

SoftwareAffected versions
Microsoft Exchange ServerServers and applications · cpe:a:microsoft:exchange_server
  • Version 2016-cumulative_update_21
  • Version 2016-cumulative_update_22
  • Version 2019-cumulative_update_10
  • Version 2019-cumulative_update_11

Known exploited

CISA name
Microsoft Exchange Server Remote Code Execution Vulnerability
Required action
Apply updates per vendor instructions.
Due for US agencies
1 Dec 2021
Used in ransomware
Yes, known

References

  • NVD https://nvd.nist.gov/vuln/detail/CVE-2021-42321
  • CVE.org https://www.cve.org/CVERecord?id=CVE-2021-42321