CVE-2018-4239 in iOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 11.4 is affected. The issue involves the "Magnifier" component. It allows physically proximate attackers to bypass the lock-screen protection mechanism and see the most recent Magnifier image.
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Analysis
by VulDB Data Team • 03/21/2023
The vulnerability identified as CVE-2018-4239 represents a significant security flaw in Apple's iOS operating system affecting versions prior to 11.4. This weakness resides within the Magnifier component, which is designed to assist users with visual impairments by enlarging content on the screen. The flaw stems from inadequate protection mechanisms surrounding the lock screen interface, creating an exploitable condition that allows unauthorized access to sensitive visual information.
The technical nature of this vulnerability falls under the category of insufficient lock screen protection, specifically related to the persistence of visual content after device lock. When the Magnifier feature is used on an iOS device, it captures and displays a magnified view of content that should normally be protected by the device's lock screen mechanism. The flaw enables attackers who are physically present and in close proximity to the device to bypass the standard lock screen protection and access the most recent image captured by the Magnifier tool. This represents a direct violation of the principle of least privilege and information hiding that should govern all operating system components.
From an operational perspective, this vulnerability creates a serious risk for users who may be in physical proximity to others, such as in public spaces, offices, or shared environments. The attack vector is particularly concerning because it requires only physical access to the device rather than sophisticated technical skills or network-based exploitation. The impact extends beyond simple privacy concerns to potentially expose sensitive personal or professional information that may have been viewed through the Magnifier tool, including documents, messages, or other visual content that was processed while the device was unlocked.
The vulnerability demonstrates a clear failure in Apple's security model for protecting user data at the interface level, particularly concerning the handling of temporary visual content that should be automatically cleared or protected when a device enters a locked state. This issue aligns with CWE-200, which addresses "Information Exposure," and reflects poor implementation of access control mechanisms within the device's user interface layer. The flaw also relates to ATT&CK technique T1557, which covers "Adversary-in-the-Middle" attacks, as it allows for unauthorized access to information that should be protected by the device's security controls. Users who rely on assistive technologies like Magnifier for visual assistance are particularly vulnerable, as the feature's design does not adequately consider the security implications of its operation in conjunction with lock screen protection mechanisms.
The recommended mitigation strategy involves immediate updating of affected iOS devices to version 11.4 or later, which contains the necessary security patches to address the lock screen protection flaw. Users should also be advised to avoid leaving their devices unattended in public spaces, particularly when using assistive technologies that may create persistent visual content. Organizations should consider implementing additional physical security measures for devices containing sensitive information and ensure that all iOS devices within their environment are maintained at current security levels. The vulnerability serves as a reminder of the importance of considering security implications during the design phase of assistive technologies and the need for comprehensive security testing that covers all user interface components, particularly those that handle temporary or transient data.