CVE-2021-30663

HIGH

8.8

CVSS Score

Published: September 8, 2021 at 02:49 PM UTC

Updated: June 17, 2026 at 03:50 AM UTC

5 products affected across 1 vendormacOSiPhone OSiPadOS

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Severity

HIGH8.8

Exploitation

CISA KEV

Exploit prediction

EPSS 4%

SSVC

Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score3.5%

EPSS (Exploit Prediction Scoring System) estimates a 3.5% chance this CVE is exploited in the wild within the next 30 days — higher than 89% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

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.

Required Action

Apply updates per vendor instructions.

Ransomware Use

Unknown

Added to KEV

Nov 3, 2021

Remediation Due

Nov 17, 2021

1809 days overdue

Notes

https://nvd.nist.gov/vuln/detail/CVE-2021-30663

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

iPadOS · Apple

95%

14.0 ≤ v < 14.5.1

Affected range stops below 14.5.1, so it looks safe — our inference, not a vendor statement

iPhone OS · Apple

95%

v < 12.5.314.0 ≤ v < 14.5.1

Affected range stops below 12.5.3, so it looks safe — our inference, not a vendor statement

Affected range stops below 14.5.1, so it looks safe — our inference, not a vendor statement

macOS · Apple

95%

v < 11.3v < 12.5v < 14.1v < 14.5v < 14.611.0 ≤ v < 11.3.1

Affected range stops below 11.3, so it looks safe — our inference, not a vendor statement

Affected range stops below 11.3.1, so it looks safe — our inference, not a vendor statement

Affected range stops below 12.5, so it looks safe — our inference, not a vendor statement

Affected range stops below 14.1, so it looks safe — our inference, not a vendor statement

Affected range stops below 14.5, so it looks safe — our inference, not a vendor statement

Affected range stops below 14.6, so it looks safe — our inference, not a vendor statement

Safari · Apple

95%

v < 14.1.1

Affected range stops below 14.1.1, so it looks safe — our inference, not a vendor statement

tvOS · Apple

95%

v < 14.6

Affected range stops below 14.6, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references