Is CVE-2021-1871 being actively exploited?

Yes. CVE-2021-1871 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added on November 3, 2021.

What is the CVSS score for CVE-2021-1871?

CVE-2021-1871 has a CVSS 3.1 base score of 9.8 (CRITICAL).

CVE-2021-1871

CRITICAL · CVSS 9.8CISA KEV: actively exploitedEPSS 7.0%EU EUVD: exploited

A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

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
EPSS score: 7.0% (94th percentile)
In CISA KEV: Yes, added November 3, 2021
In EU EUVD: Yes (EUVD-2021-7335)
Published: April 2, 2021
NVD last modified: June 17, 2026
Status: Analyzed

CISA Known Exploited Vulnerability

Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability

Added to the KEV catalog on November 3, 2021; federal remediation due November 17, 2021.

EU Vulnerability Database (EUVD)

This vulnerability is also tracked by ENISA as EUVD-2021-7335 in the EU Vulnerability Database. ENISA flags it as known exploited. Last updated in EUVD on October 21, 2025.

View on the EU Vulnerability Database

Affected products

apple / ipados
apple / iphone os
apple / mac os x
apple / mac os x
apple / mac os x
apple / mac os x
apple / macos
debian / debian linux
fedoraproject / fedora

Certified products that may be affected

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

Apple macOS 11 Big Sur: Contacts - Apple Inc. - Common Criteria CCEVS-VR-VID-11243-2022 - archived

References

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L3L6ZZOU5JS7E3RFYGLP7UFLXCG7TNLU/(Broken Link, Mailing List)
https://support.apple.com/en-us/HT212146(Release Notes, Vendor Advisory)
https://support.apple.com/en-us/HT212147(Release Notes, Vendor Advisory)
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-1871(US Government Resource)
https://www.debian.org/security/2021/dsa-4923(Mailing List, Third Party Advisory)

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

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