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CVE-2023-21709: Microsoft Exchange Server Elevation of Privilege Vulnerability

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-08-08 · updated 2026-08-10
• Weakness: CWE-307

Description

Microsoft Exchange Server Elevation of Privilege Vulnerability

Affected products

• Microsoft Exchange Server: 2016-cumulative_update_1, 2016-cumulative_update_10, 2016-cumulative_update_11, 2016-cumulative_update_12, 2016-cumulative_update_13, 2016-cumulative_update_14 (+27); 2016, 2019
• Microsoft Exchange Server 2016 Cumulative Update 23: from 15.01.0 before 15.01.2507.032 — fixed in 15.01.2507.032
• Microsoft Exchange Server 2019 Cumulative Update 12: from 15.02.0 before 15.02.1118.037 — fixed in 15.02.1118.037
• Microsoft Exchange Server 2019 Cumulative Update 13: from 15.02.0 before 15.02.1258.025 — fixed in 15.02.1258.025

How to fix

Upgrade to a fixed version: Microsoft Exchange Server 2016 Cumulative Update 23 15.01.2507.032; Microsoft Exchange Server 2019 Cumulative Update 12 15.02.1118.037; Microsoft Exchange Server 2019 Cumulative Update 13 15.02.1258.025. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21709
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21709

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