Apple iOS/iPadOS up to 12.5.2/14.5.0 WebKit integer overflow

Summaryinfo

A vulnerability, which was classified as critical, has been found in Apple iOS and iPadOS up to 12.5.2/14.5.0. The impacted element is an unknown function of the component WebKit. This manipulation causes integer overflow. This vulnerability is handled as CVE-2021-30663. The attack can be initiated remotely. Additionally, an exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Apple iOS and iPadOS up to 12.5.2/14.5.0 (Smartphone Operating System). Affected by this vulnerability is an unknown functionality of the component WebKit. The manipulation with an unknown input leads to a integer overflow vulnerability. The CWE definition for the vulnerability is CWE-190. The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

The weakness was released 05/03/2021 as HT212341 as confirmed advisory (Website). It is possible to read the advisory at support.apple.com. This vulnerability is known as CVE-2021-30663. It demands that the victim is doing some kind of user interaction. Technical details are unknown but a private exploit is available. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 07/29/2025). It is expected to see the exploit prices for this product increasing in the near future. The advisory points out:

Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited.

It is declared as attacked. The vulnerability scanner Nessus provides a plugin with the ID 241427 (RHEL 7 : webkitgtk4 (RHSA-2025:10364)), which helps to determine the existence of the flaw in a target environment. The CISA Known Exploited Vulnerabilities Catalog lists this issue since 11/03/2021 with a due date of 11/17/2021:

Apply updates per vendor instructions.

Upgrading to version 12.5.3 or 14.5.1 eliminates this vulnerability. A possible mitigation has been published immediately after the disclosure of the vulnerability. The advisory contains the following remark:

An integer overflow was addressed with improved input validation.

The vulnerability is also documented in the databases at Zero-Day.cz (626), Tenable (241427) and EUVD (EUVD-2021-17580). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Smartphone Operating System

Vendor

• Apple

Name

• iOS
• iPadOS

Version

• 12.5.0
• 12.5.1
• 12.5.2
• 14.0
• 14.1
• 14.2
• 14.3
• 14.4
• 14.5.0

License

• commercial

Website

• Vendor: https://www.apple.com/

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