Apple · iOS, iPadOS, and macOS
CVE-2021-1871
Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability
What it is
A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..
CISA: Apple iOS, iPadOS, and macOS WebKit contain an unspecified logic vulnerability that allows a remote attacker to execute code. 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 |
|---|---|---|---|---|
| Aug 21, 2025 | Out-of-Bounds Write | iOS, iPadOS, and macOS | Critical 10.0 | 65% |
| Sep 11, 2023 | ImageIO Buffer Overflow | iOS, iPadOS, and macOS | High 7.8 | 53% |
| Apr 10, 2023 | IOSurfaceAccelerator Out-of-Bounds Write | iOS, iPadOS, and macOS | High 8.6 | 23% |
| Mar 30, 2023 | Out-of-Bounds Write | iOS, iPadOS, and macOS | High 7.8 | 5.2% |
| Sep 14, 2022 | Remote Code Execution | iOS, iPadOS, and macOS | High 7.8 | 5.6% |
| Sep 8, 2022 | Input Validation | iOS, iPadOS, and macOS | Medium 5.5 | 3.2% |
| Feb 11, 2022 | Webkit Use-After-Free | iOS, iPadOS, and macOS | High 8.8 | 16% |
| Nov 3, 2021 | WebKit Remote Code Execution | iOS, iPadOS, and macOS | Critical 9.8 | 7.7% |
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.