CVE-2021-30663VulnerabilityPublished 11/03/2021Updated 10/24/2026

CVE-2021-30663: Apple Multiple Products WebKit Integer Overflow Vulnerability

Affects Apple Multiple ProductsSource CISA KEV

Severity

High

No CVSS score published yet

Exploitation: Actively exploited – in CISA KEV since 11/03/2021
KEV deadline: 11/17/2021
EPSS: 3.5% chance of exploitation in 30 days – higher than 89% of CVEs

What to do

CISA required action

Apply updates per vendor instructions.

nvd.nist.gov/vuln/detail/CVE-2021-30663 (opens in a new tab)

Description

An integer overflow vulnerability exists in Apple WebKit used by iOS, iPadOS, macOS, tvOS, and Safari. This flaw allows code execution when processing specially crafted web content. The vulnerability affects HTML parsers relying on WebKit, including Apple Safari and potentially other products using WebKit. Exploitation in the wild has been confirmed. No explicit affected versions or patch information is provided.

Summary

CVE-2021-30663 is an integer overflow vulnerability in Apple WebKit that can lead to arbitrary code execution when processing malicious web content. The issue affects multiple Apple platforms including iOS, iPadOS, macOS, tvOS, and Safari browser. The vulnerability impacts HTML parsers that use WebKit, which may include non-Apple products that rely on WebKit for HTML processing. Exploits have been observed in the wild, indicating active threat. No vendor advisory or patch details are included in the provided data.

Impact

Successful exploitation allows remote attackers to execute arbitrary code on affected devices by delivering crafted web content. This can lead to compromise of user devices running vulnerable versions of Apple WebKit-based software. The presence of known exploits in the wild increases the urgency and risk of exploitation.

Mitigation

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Users and administrators should monitor official Apple security updates and apply patches promptly once available. Until a fix is confirmed, avoid visiting untrusted websites or opening suspicious web content on affected Apple products.

CVE-2021-30663: Apple Multiple Products WebKit Integer Overflow Vulnerability

What to do

Description

Summary

Impact

Mitigation

Weaknesses

References

What to do

Description

AnalysisAI-generated, updated 10/24/2026, 09:40:50 UTC

Weaknesses

References

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