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CVE-2023-21761: Microsoft Exchange Server Information Disclosure Vulnerability

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-01-10 · updated 2026-06-17
• Weakness: CWE-918

Description

Microsoft Exchange Server Information Disclosure Vulnerability

Affected products

• Microsoft Exchange Server: 2016-cumulative_update_23, 2019-cumulative_update_11, 2019-cumulative_update_12
• Microsoft Exchange Server 2016 Cumulative Update 23: from 15.01.0 before 15.01.2507.017 — fixed in 15.01.2507.017
• Microsoft Exchange Server 2019 Cumulative Update 11: from 15.02.0 before 15.02.0986.037 — fixed in 15.02.0986.037
• Microsoft Exchange Server 2019 Cumulative Update 12: from 15.02.0 before 15.02.1118.021 — fixed in 15.02.1118.021

How to fix

Upgrade to a fixed version: Microsoft Exchange Server 2016 Cumulative Update 23 15.01.2507.017; Microsoft Exchange Server 2019 Cumulative Update 11 15.02.0986.037; Microsoft Exchange Server 2019 Cumulative Update 12 15.02.1118.021. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21761
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21761

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