Apple · Multiple Products
CVE-2021-30663
Apple Multiple Products WebKit Integer Overflow Vulnerability
What it is
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.
CISA: Apple iOS, iPadOS, macOS, tvOS, and Safari WebKit contain an integer overflow vulnerability that leads to code execution when processing maliciously crafted web content. This vulnerability could impact HTML parsers that use WebKit, including but not limited to Apple Safari and non-Apple products which rely on WebKit for HTML processing.
What to do
Apply updates per vendor instructions.
Deadline for US federal agencies: November 17, 2021
More exploited flaws from Apple
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Sep 29, 2026 | Out-of-Bounds Write | Multiple Products | High 8.8 | 26% |
| Mar 20, 2026 | Buffer Overflow | Multiple Products | High 8.8 | 1.7% |
| Mar 20, 2026 | Improper Locking | Multiple Products | High 7.8 | 0.4% |
| Mar 20, 2026 | Classic Buffer Overflow | Multiple Products | Medium 5.5 | 0.4% |
| Mar 5, 2026 | Integer Overflow or Wraparound | Multiple Products | High 8.8 | 7.0% |
| Mar 5, 2026 | Use-After-Free | Multiple Products | High 8.8 | 4.0% |
| Feb 12, 2026 | Multiple Buffer Overflow | Multiple Products | High 7.8 | 1.7% |
| Dec 15, 2025 | Use-After-Free WebKit | Multiple Products | High 8.8 | 26% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.