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CVE-2021-26858

Microsoft Exchange Server Remote Code Execution Vulnerability

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

Severity
High 7.8
Published
3 Mar 2021
Last changed
1 Oct 2026
Added to UpHeron
1 Nov 2026
Sources
NVD

Affected software

SoftwareAffected versions
Microsoft Exchange ServerServers and applications · cpe:a:microsoft:exchange_server
  • Version 2019-cumulative_update_8
  • Version 2019-cumulative_update_7
  • Version 2019-cumulative_update_6
  • Version 2019-cumulative_update_5
All 24 release lines
  • Version 2013-cumulative_update_21
  • Version 2013-cumulative_update_22
  • Version 2013-cumulative_update_23
  • Version 2016-cumulative_update_8
  • Version 2016-cumulative_update_9
  • Version 2016-cumulative_update_10
  • Version 2016-cumulative_update_11
  • Version 2016-cumulative_update_12
  • Version 2016-cumulative_update_13
  • Version 2016-cumulative_update_14
  • Version 2016-cumulative_update_15
  • Version 2016-cumulative_update_16
  • Version 2016-cumulative_update_17
  • Version 2016-cumulative_update_18
  • Version 2016-cumulative_update_19
  • Version 2019
  • Version 2019-cumulative_update_1
  • Version 2019-cumulative_update_2
  • Version 2019-cumulative_update_3
  • Version 2019-cumulative_update_4
  • Version 2019-cumulative_update_5
  • Version 2019-cumulative_update_6
  • Version 2019-cumulative_update_7
  • Version 2019-cumulative_update_8

Known exploited

CISA name
Microsoft Exchange Server Remote Code Execution Vulnerability
Required action
Apply updates per vendor instructions.
Due for US agencies
3 May 2022
Used in ransomware
Yes, known

References

  • NVD https://nvd.nist.gov/vuln/detail/CVE-2021-26858
  • CVE.org https://www.cve.org/CVERecord?id=CVE-2021-26858