CVE-2021-1878: Apple Mac OS X

Medium severity, CVSS 6.5. EPSS: 1.8% chance of exploitation in the next 30 days.

An integer overflow was addressed with improved input validation. This issue is fixed in macOS Big Sur 11.3, Security Update 2021-002 Catalina, Security Update 2021-003 Mojave. An attacker in a privileged network position may be able to leak sensitive user information.

Affected products

• Apple Mac OS X: from 10.14, up to and including 10.14.5; from 10.15, up to and including 10.15.5; version 10.14.6 only; version 10.15.6 only; version 10.15.7 only
• Apple macOS: from 11.0, before 11.3 (fixed in 11.3)

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