CVE-2021-30666: Apple iOS WebKit Buffer Overflow Vulnerability

High severity, CVSS 8.8. Actively exploited: in CISA KEV since 2021-11-03. EPSS: 3% chance of exploitation in the next 30 days.

A buffer overflow issue was addressed with improved memory handling. This issue is fixed in iOS 12.5.3. Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

Affected products

• Apple iPhone OS: before 12.5.3 (fixed in 12.5.3)

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