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CVE-2021-34523

Microsoft Exchange Server Elevation of Privilege Vulnerability

Actively exploited: CISA added it to its Known Exploited Vulnerabilities catalog on 3 Nov 2021.

Severity
Critical 9.0
Published
14 Jul 2021
Last changed
10 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 2013-cumulative_update_23
  • Version 2016-cumulative_update_19
  • Version 2016-cumulative_update_20
  • Version 2019-cumulative_update_8
  • Version 2019-cumulative_update_9

Known exploited

CISA name
Microsoft Exchange Server Privilege Escalation Vulnerability
Required action
Apply updates per vendor instructions.
Due for US agencies
17 Nov 2021
Used in ransomware
Yes, known

References

  • NVD https://nvd.nist.gov/vuln/detail/CVE-2021-34523
  • CVE.org https://www.cve.org/CVERecord?id=CVE-2021-34523