CVE-2021-1840: Apple Mac OS X

High severity, CVSS 7.8. EPSS: 0.3% chance of exploitation in the next 30 days.

A memory corruption issue was addressed with improved validation. This issue is fixed in macOS Big Sur 11.3, Security Update 2021-002 Catalina, Security Update 2021-003 Mojave. A local attacker may be able to elevate their privileges.

Affected products

• Apple Mac OS X: version 10.14 only; version 10.14.0 only; version 10.14.1 only; version 10.14.2 only; version 10.14.3 only; version 10.14.4 only; …
• Apple macOS: from 11.0, before 11.3 (fixed in 11.3)

Published 2021-09-08. Last modified 2026-06-17.