Is CVE-2020-9866 being actively exploited?

CVE-2020-9866 is not currently listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

What is the CVSS score for CVE-2020-9866?

CVE-2020-9866 has a CVSS 3.1 base score of 9.8 (CRITICAL).

CVE-2020-9866

CRITICAL · CVSS 9.8EPSS 1.9%EU EUVD

A buffer overflow was addressed with improved bounds checking. This issue is fixed in macOS Catalina 10.15.6, Security Update 2020-004 Mojave, Security Update 2020-004 High Sierra. A buffer overflow may result in arbitrary code execution.

Key facts

CVSS score: 9.8 (v3.1)
Severity: CRITICAL
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-120
EPSS score: 1.9% (80th percentile)
In CISA KEV: No
In EU EUVD: Yes (EUVD-2020-30645)
Published: October 27, 2020
NVD last modified: June 17, 2026
Status: Modified

EU Vulnerability Database (EUVD)

This vulnerability is also tracked by ENISA as EUVD-2020-30645 in the EU Vulnerability Database. Last updated in EUVD on August 4, 2024.

View on the EU Vulnerability Database

Affected products

apple / mac os x

Certified products that may be affected

2 FIPS 140 or Common Criteria certified products, from automated matching by sec-certs.org.

Apple Mac OS X 10.6 - Apple Inc. - Common Criteria BSI-DSZ-CC-0536-2010 - archived
Apple Mac OS X v10.3.6 and Apple Mac OS X Server V10.3.6 - Apple Inc. - Common Criteria CCEVS-VR-0086-2005 - archived

References

https://support.apple.com/en-us/HT211289(Release Notes, Vendor Advisory)

Last updated September 17, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS

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