What’s Vulnerable › Vulnerabilities

CVE-2021-31198: Microsoft Exchange Server Remote Code Execution Vulnerability

• Severity: medium (CVSS 6.8 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 4.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-05-11 · updated 2026-06-17
• Weakness: CWE-20

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 15.00.1497.018 — fixed in 15.00.1497.018
• Microsoft Exchange Server 2016 Cumulative Update 19: from 15.01.0 before 15.01.2176.014 — fixed in 15.01.2176.014
• Microsoft Exchange Server 2016 Cumulative Update 20: from 15.01.0 before 15.01.2242.010 — fixed in 15.01.2242.010
• Microsoft Exchange Server 2019 Cumulative Update 8: from 15.02.0 before 15.02.0792.015 — fixed in 15.02.0792.015
• Microsoft Exchange Server 2019 Cumulative Update 9: from 15.02.0 before 15.02.0858.012 — fixed in 15.02.0858.012

How to fix

Upgrade to a fixed version: Microsoft Exchange Server 2013 Cumulative Update 23 15.00.1497.018; Microsoft Exchange Server 2016 Cumulative Update 19 15.01.2176.014; Microsoft Exchange Server 2016 Cumulative Update 20 15.01.2242.010; Microsoft Exchange Server 2019 Cumulative Update 8 15.02.0792.015; Microsoft Exchange Server 2019 Cumulative Update 9 15.02.0858.012. Check the vendor advisory for mitigations.

References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31198
• https://www.zerodayinitiative.com/advisories/ZDI-21-894/
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31198
• https://www.zerodayinitiative.com/advisories/ZDI-21-894/

Get alerted when CVE-2021-31198 or the next vulnerability affects your stack