CVE-2021-1871: Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability

Critical severity, CVSS 9.8. Actively exploited: in CISA KEV since 2021-11-03. EPSS: 7% chance of exploitation in the next 30 days.

A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

Affected products

• Apple iPadOS: before 14.4 (fixed in 14.4)
• Apple iPhone OS: before 14.4 (fixed in 14.4)
• Apple Mac OS X: from 10.15, before 10.15.7 (fixed in 10.15.7); version 10.15.7 only
• Apple macOS: from 11.0.1, before 11.2 (fixed in 11.2)
• Debian Debian Linux: version 10.0 only
• Fedoraproject Fedora: version 33 only

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