CVE-2021-1821: Apple macOS

Medium severity, CVSS 6.5. EPSS: 0.7% chance of exploitation in the next 30 days.

A logic issue was addressed with improved state management. This issue is fixed in watchOS 7.6, macOS Big Sur 11.5. Visiting a maliciously crafted webpage may lead to a system denial of service.

Affected products

• Apple macOS: before 11.5 (fixed in 11.5)
• Apple watchOS: before 7.6 (fixed in 7.6)

Published 2021-10-28. Last modified 2026-06-17.