CVE-2021-1771: Apple Mac OS X

Low severity, CVSS 3.3. EPSS: 0.5% chance of exploitation in the next 30 days.

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.

Affected products

• Apple Mac OS X: from 10.14, before 10.14.6 (fixed in 10.14.6); from 10.15, before 10.15.7 (fixed in 10.15.7); version 10.14.6 only; version 10.15.7 only
• Apple macOS: from 11.0, before 11.2 (fixed in 11.2)

Published 2021-04-02. Last modified 2026-06-17.