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CVE-2021-26412: Microsoft Exchange Server Remote Code Execution Vulnerability

• Severity: medium (CVSS 6.5 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 33.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-03-02 · updated 2026-08-19

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

Affected products

• Microsoft Exchange Server: 2013-cumulative_update_23, 2016-cumulative_update_18, 2016-cumulative_update_19, 2019-cumulative_update_7, 2019-cumulative_update_8
• Microsoft Exchange Server 2013 Cumulative Update 23: from 15.00.0 before 15.00.1497.012 — fixed in 15.00.1497.012
• Microsoft Exchange Server 2016 Cumulative Update 18: from 15.01.0 before 15.01.2106.013 — fixed in 15.01.2106.013
• Microsoft Exchange Server 2016 Cumulative Update 19: from 15.01.0 before 15.01.2176.009 — fixed in 15.01.2176.009
• Microsoft Exchange Server 2019 Cumulative Update 7: from 15.02.0 before 15.02.0721.013 — fixed in 15.02.0721.013
• Microsoft Exchange Server 2019 Cumulative Update 8: from 15.02.0 before 15.02.0792.010 — fixed in 15.02.0792.010

How to fix

Upgrade to a fixed version: Microsoft Exchange Server 2013 Cumulative Update 23 15.00.1497.012; Microsoft Exchange Server 2016 Cumulative Update 18 15.01.2106.013; Microsoft Exchange Server 2016 Cumulative Update 19 15.01.2176.009; Microsoft Exchange Server 2019 Cumulative Update 7 15.02.0721.013; Microsoft Exchange Server 2019 Cumulative Update 8 15.02.0792.010. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26412
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26412

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