Priority reviewHigh

CVE-2021-31206

Microsoft Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Exchange Server 2016 Cumulative Update 20, Microsoft Exchange Server 2016 Cumulative Update 21

CVE-2021-31206 affects Microsoft Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Exchange Server 2016 Cumulative Update 20, Microsoft Exchange Server 2016 Cumulative Update 21. Review the CVSS score, exploitation signals, affected versions, remediation status, and linked source material before making a change.

CVSS: 8
EPSS: 13.0%
CISA KEV: Not listed
Published: 2021.07.15

PRIORITY ASSESSMENT

Priority review

FIRST EPSS indicates an elevated probability of exploitation.

Known exploitationNot established by KEV

Exploit probability13.0%

Technical severityCVSS 8

Vulnerability overview

Affected product and versions

Product: Microsoft Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Exchange Server 2016 Cumulative Update 20, Microsoft Exchange Server 2016 Cumulative Update 21
Affected versions: >= 15.00.0 < 15.00.1497.023, >= 15.01.0 < 15.01.2242.012, >= 15.01.0 < 15.01.2308.014, >= 15.02.0 < 15.02.0922.013, >= 15.02.0 < 15.02.0858.015, 2013, 2016, 2019
Fixed versions: No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that Microsoft Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Exchange Server 2016 Cumulative Update 20, Microsoft Exchange Server 2016 Cumulative Update 21 and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CWE: Not available