CVE-2021-30663: Apple Multiple Products WebKit Integer Overflow Vulnerability

High severity, CVSS 8.8. Actively exploited: in CISA KEV since 2021-11-03. EPSS: 3.5% chance of exploitation in the next 30 days.

An integer overflow was addressed with improved input validation. This issue is fixed in iOS 14.5.1 and iPadOS 14.5.1, tvOS 14.6, iOS 12.5.3, Safari 14.1.1, macOS Big Sur 11.3.1. Processing maliciously crafted web content may lead to arbitrary code execution.

Affected products

• Apple iPadOS: from 14.0, before 14.5.1 (fixed in 14.5.1)
• Apple iPhone OS: before 12.5.3 (fixed in 12.5.3); from 14.0, before 14.5.1 (fixed in 14.5.1)
• Apple macOS: from 11.0, before 11.3.1 (fixed in 11.3.1)
• Apple Safari: before 14.1.1 (fixed in 14.1.1)
• Apple tvOS: before 14.6 (fixed in 14.6)

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