What’s Vulnerable › Vulnerabilities

CVE-2023-21529: Microsoft Exchange Server Remote Code Execution Vulnerability

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2026-04-13
• EPSS: 59.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-02-14 · updated 2026-08-19
• Weakness: CWE-502

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

Affected products

• Microsoft Exchange Server: 2013-cumulative_update_23, 2016-cumulative_update_23, 2019-cumulative_update_11, 2019-cumulative_update_12
• Microsoft Exchange Server 2013 Cumulative Update 23: from 15.00.0 before 15.00.1497.047 — fixed in 15.00.1497.047
• Microsoft Exchange Server 2016 Cumulative Update 23: from 15.01.0 before 15.01.2507.021 — fixed in 15.01.2507.021
• Microsoft Exchange Server 2019 Cumulative Update 11: from 15.02.0 before 15.02.0986.041 — fixed in 15.02.0986.041
• Microsoft Exchange Server 2019 Cumulative Update 12: from 15.02.0 before 15.02.1118.025 — fixed in 15.02.1118.025

How to fix

Upgrade to a fixed version: Microsoft Exchange Server 2013 Cumulative Update 23 15.00.1497.047; Microsoft Exchange Server 2016 Cumulative Update 23 15.01.2507.021; Microsoft Exchange Server 2019 Cumulative Update 11 15.02.0986.041; Microsoft Exchange Server 2019 Cumulative Update 12 15.02.1118.025. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-21529
• https://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/

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