CVE-2021-30663

Name: CVE-2021-30663
Creator: NVD / NIST
Published: 2021-09-08T15:15:13.413+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10Actively ExploitedEPSS 3.47%

Last modified Jun 17, 2026

CVE-2021-30663 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. 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. CISA has confirmed active exploitation in the wild. EPSS estimates a 3.47% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

8.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS Probability

3.47%

87.6th percentile

Probability of exploitation in the next 30 days. Learn more

Exploitation Status

This vulnerability is listed in CISA’s Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. Federal agencies must remediate by Nov 17, 2021.

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Apple	Safari	< 14.1.1
Apple	Ipados	>= 14.0, < 14.5.1
Apple	Iphone Os	< 12.5.3
Apple	Iphone Os	>= 14.0, < 14.5.1
Apple	Macos	>= 11.0, < 11.3.1
Apple	Tvos	< 14.6

References

https://support.apple.com/en-us/HT212335Release Notes, Vendor Advisory
https://support.apple.com/en-us/HT212336Release Notes, Vendor Advisory
https://support.apple.com/en-us/HT212341Release Notes, Vendor Advisory
https://support.apple.com/en-us/HT212532Release Notes, Vendor Advisory
https://support.apple.com/en-us/HT212534Release Notes, Vendor Advisory
https://support.apple.com/en-us/HT212335Release Notes, Vendor Advisory
https://support.apple.com/en-us/HT212336Release Notes, Vendor Advisory
https://support.apple.com/en-us/HT212341Release Notes, Vendor Advisory
https://support.apple.com/en-us/HT212532Release Notes, Vendor Advisory
https://support.apple.com/en-us/HT212534Release Notes, Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-30663Third Party Advisory, US Government Resource

Timeline

Published: Sep 8, 2021
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2021-30663?

How severe is CVE-2021-30663?

CVE-2021-30663 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 3.47% probability of exploitation in the next 30 days. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog.

How do I fix CVE-2021-30663?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-30663?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST