Is CVE-2021-31198 in the CISA KEV catalog?

No. CVE-2021-31198 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-31198?

CVE-2021-31198 has a CVSS v3 base score of 7.8 (HIGH).

What is the EPSS score for CVE-2021-31198?

CVE-2021-31198 has an EPSS score of 4.87% (91th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-31198?

Install KB5003435 for Microsoft Exchange Server 2013 Cumulative Update 23. Fixes are available for 5 affected products.

CVE & CISA-KEV Catalog

CVE-2021-31198

HIGHEPSS 91th pctl

7.8

CVSS v3

NVD

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

CWE-20Improper Input Validation CWE-94Code Injection

How to fix

Remediation Available

Microsoft Exchange Server 2013 Cumulative Update 23Microsoft

Install:KB5003435Microsoft

Microsoft Exchange Server 2016 Cumulative Update 19Microsoft

Install:KB5003435Microsoft

Microsoft Exchange Server 2016 Cumulative Update 20Microsoft

Install:KB5003435Microsoft

Microsoft Exchange Server 2019 Cumulative Update 8Microsoft

Install:KB5003435Microsoft

Microsoft Exchange Server 2019 Cumulative Update 9Microsoft

Install:KB5003435Microsoft

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorLocal

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Exploit Intelligence

4.87%probability of exploitation in 30 days

91stpercentile

High risk: more likely to be exploited than 91% of all known CVEs.

References

Patch1

portal.msrc.microsoft.com

Third-Party Advisory1

zerodayinitiative.com

Related Vulnerabilities

Other CWE-20 (Improper Input Validation) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-3400	Critical	10.0	100%	KEV + Ransom	-
CVE-2021-45105	Medium	5.9	100%	-	Fix
CVE-2021-44228	Critical	10.0	100%	KEV + Ransom	Fix
CVE-2021-21985	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2018-7600	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2020-3452	High	7.5	100%	KEV	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-02-28.