What is CVE-2021-1771?

CVE-2021-1771 is a low-severity vulnerability in Apple macOS. CVSS score: 3.3/10. Published 2021-04-02.

How severe is CVE-2021-1771?

Low severity. CVSS v3 base score is 3.3 out of 10.

Vulnerability in Apple macOS

CVE-2021-1771

This issue was addressed with improved checks. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave. A user that is removed from an iMessage group could rejoin the group.

Published 2021-04-02 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 3.3 (Low). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.005 (43.5th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 43.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Apple macOS — versions unspecified
Apple Mac OS X — versions 10.14.6, 10.15.7

References

support.apple.com/en-us/HT212147 (Release Notes, Vendor Advisory)

Frequently asked questions

What is CVE-2021-1771?: CVE-2021-1771 is a low-severity vulnerability in Apple macOS. CVSS score: 3.3/10. Published 2021-04-02.
How severe is CVE-2021-1771?: Low severity. CVSS v3 base score is 3.3 out of 10.