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CVE-2021-34470: Microsoft Exchange Server Elevation of Privilege Vulnerability

• Severity: medium (CVSS 5.2 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 4.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-07-14 · updated 2026-08-10

Description

Microsoft Exchange Server Elevation of Privilege Vulnerability

Affected products

• Microsoft Exchange Server: 2013-cumulative_update_23, 2016-cumulative_update_21, 2019-cumulative_update_10
• Microsoft Exchange Server 2013 Cumulative Update 23: from 15.00.0 before 15.00.1497.023 — fixed in 15.00.1497.023
• Microsoft Exchange Server 2016 Cumulative Update 21: from 15.01.0 before 15.01.2308.008 — fixed in 15.01.2308.008
• Microsoft Exchange Server 2019 Cumulative Update 10: from 15.02.0 before 15.02.0922.007 — fixed in 15.02.0922.007

How to fix

Upgrade to a fixed version: Microsoft Exchange Server 2013 Cumulative Update 23 15.00.1497.023; Microsoft Exchange Server 2016 Cumulative Update 21 15.01.2308.008; Microsoft Exchange Server 2019 Cumulative Update 10 15.02.0922.007. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34470
• http://packetstormsecurity.com/files/163706/Microsoft-Exchange-AD-Schema-Misconfiguration-Privilege-Escalation.html
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34470

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