Apple iOS WebKit Buffer Overflow Vulnerability
Apple iOS WebKit contains a buffer-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.
- Vendor
- Apple
- Product
- iOS
- CVSS
- 8.8
- EPSS (exploit probability)
- 3.0%
- Status
- kev
- CISA patch-by (BOD 22-01)
- Added to KEV
Is CVE-2021-30666 being exploited?
Yes. CISA added CVE-2021-30666 to its Known Exploited Vulnerabilities catalog on . CISA only lists a CVE when it has reliable evidence of exploitation in the wild.
FIRST's EPSS model puts the probability of exploitation activity in the next 30 days at 3.0% (scored October 14, 2026).
- CISA KEV[ LISTED ]
- ENISA EUVD (exploited)[ — ]
- CIRCL KEV[ — ]
Catalog snapshot 2026-10-21. Full cross-catalog view: /kev-comparison
What to do
CISA required actionApply updates per vendor instructions.
US federal civilian agencies must remediate by (14 days after listing) under BOD 22-01. Everyone else: that deadline is a sensible upper bound, not a target. Vendor guidance and the NVD record are linked under Source above.
Other Apple iOS CVEs we track
| CVE / Vulnerability | Severity | CVSS | EPSS | Added to KEV |
|---|---|---|---|---|
| CVE-2022-42856 Apple iOS Type Confusion Vulnerability | [ HIGH ] | 8.8 | 8.5% | |
| CVE-2016-4657 Apple iOS Webkit Memory Corruption Vulnerability | [ HIGH ] | 8.8 | 66.8% | |
| CVE-2016-4656 Apple iOS Memory Corruption Vulnerability | [ HIGH ] | 7.8 | 23.6% | |
| CVE-2016-4655 Apple iOS Information Disclosure Vulnerability | [ MEDIUM ] | 5.5 | 33.4% | |
| CVE-2019-7287 Apple iOS Memory Corruption Vulnerability | [ HIGH ] | 7.8 | 4.6% | |
| CVE-2021-30762 Apple iOS WebKit Use-After-Free Vulnerability | [ HIGH ] | 8.8 | 11.0% | |
| CVE-2021-30761 Apple iOS WebKit Memory Corruption Vulnerability | [ HIGH ] | 8.8 | 10.5% |