CVE-2021-30666: Apple iOS WebKit Buffer Overflow Vulnerability
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..
Published Sep 8, 2021 · Updated Jun 17, 2026
Required action
Apply updates per vendor instructions.
Advisory details
From the National Vulnerability Database. This product uses the NVD API but is not endorsed or certified by the NVD.
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..
References
How this page is made: the data panel comes from the GitHub Advisory Database, CISA’s KEV catalog, the NVD and FIRST EPSS, and updates twice a day. No analysis has been written for this entry yet. Methodology
More Apple vulnerabilities
All Apple entriesCVE-2026-86950
Apple Multiple Products Out-of-Bounds Write Vulnerability
high8.8ExploitedSep 28, 2026CVE-2026-65400
Apple macOS Improper Authentication Vulnerability
critical9.8ExploitedAug 6, 2026CVE-2026-20700
Apple Multiple Buffer Overflow Vulnerability
high7.8ExploitedFeb 11, 2026CVE-2025-43529
Apple Multiple Products Use-After-Free WebKit Vulnerability
high8.8ExploitedDec 17, 2025CVE-2025-43510
Apple Multiple Products Improper Locking Vulnerability
high7.8ExploitedDec 12, 2025CVE-2025-43520
Apple Multiple Products Classic Buffer Overflow Vulnerability
medium5.5ExploitedDec 12, 2025