CVE-2023-21529

Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Exchange Server 2016 Cumulative Update 23, Microsoft Exchange Server 2019 Cumulative Update 11

Published 14 Feb 2023 · updated 19 Aug 2026 · Analyzed

8.8 High · CVSS 3.1, microsoft.com

Exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on 13 Apr 2026, with a remediation deadline of 27 Apr 2026 for US federal agencies. It has been used in ransomware campaigns.

Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529 · Patch, Vendor Advisory
www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-21529 · US Government Resource
www.microsoft.com/en-us/security/blog/2026/04/06/storm-1175-focuses-gaze-on-vulnerable-web-facing-assets-in-high-tempo-medusa-ransomware-operations/ · Technical Description