CVE-2018-4221: Apple iPhone OS

High severity, CVSS 7.5. EPSS: 1.2% chance of exploitation in the next 30 days.

An issue was discovered in certain Apple products. iOS before 11.4 is affected. macOS before 10.13.5 is affected. The issue involves the "Security" component. It allows web sites to track users by leveraging the transmission of S/MIME client certificates.

Affected products

• Apple iPhone OS: before 11.4 (fixed in 11.4)
• Apple Mac OS X: before 10.13.5 (fixed in 10.13.5)

Published 2018-06-08. Last modified 2026-06-17.