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CVE-2021-28481: Microsoft Exchange Server Remote Code Execution Vulnerability

• Severity: critical (CVSS 10.0 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 36.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-04-13 · updated 2026-06-17

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

Affected products

• Microsoft Exchange Server: 2013-cumulative_update_23, 2016-cumulative_update_19, 2016-cumulative_update_20, 2019-cumulative_update_8, 2019-cumulative_update_9
• Microsoft Exchange Server 2013 Cumulative Update 23: from 15.00.0 before 15.00.1497.015 — fixed in 15.00.1497.015
• Microsoft Exchange Server 2016 Cumulative Update 19: from 15.01.0 before 15.01.2176.012 — fixed in 15.01.2176.012
• Microsoft Exchange Server 2016 Cumulative Update 20: from 15.01.0 before 15.01.2242.008 — fixed in 15.01.2242.008
• Microsoft Exchange Server 2019 Cumulative Update 8: from 15.02.0 before 15.02.0792.013 — fixed in 15.02.0792.013
• Microsoft Exchange Server 2019 Cumulative Update 9: from 15.02.0 before 15.02.0858.010 — fixed in 15.02.0858.010

How to fix

Upgrade to a fixed version: Microsoft Exchange Server 2013 Cumulative Update 23 15.00.1497.015; Microsoft Exchange Server 2016 Cumulative Update 19 15.01.2176.012; Microsoft Exchange Server 2016 Cumulative Update 20 15.01.2242.008; Microsoft Exchange Server 2019 Cumulative Update 8 15.02.0792.013; Microsoft Exchange Server 2019 Cumulative Update 9 15.02.0858.010. Check the vendor advisory for mitigations.

References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-28481
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-28481

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