CVE-2018-4391 in watchOS
Summary
by MITRE • 10/28/2020
An inconsistent user interface issue was addressed with improved state management. This issue is fixed in macOS High Sierra 10.13.1, Security Update 2017-001 Sierra, and Security Update 2017-004 El Capitan, watchOS 4.3, iOS 12.1. Processing a maliciously crafted text message may lead to UI spoofing.
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Analysis
by VulDB Data Team • 11/27/2020
The vulnerability identified as CVE-2018-4391 represents a significant user interface inconsistency that could be exploited to manipulate the visual presentation of applications on Apple devices. This issue stems from inadequate state management within the operating system's graphical user interface components, creating opportunities for malicious actors to craft text messages that could alter how interfaces appear to users. The vulnerability affects multiple Apple operating systems including macOS High Sierra 10.13.1, iOS 12.1, watchOS 4.3, and specific security updates for Sierra and El Capitan. The root cause of this vulnerability aligns with CWE-691, which addresses insufficient control flow management in user interfaces, where the system fails to properly validate or manage the state transitions of graphical elements during message processing.
The technical flaw manifests when the system processes maliciously crafted text messages that contain embedded formatting or control characters designed to manipulate the user interface state. This type of vulnerability falls under the ATT&CK framework category of T1059.007 for Command and Scripting Interpreter: PowerShell, though in this case the manipulation occurs through text message processing rather than direct command execution. The inconsistent state management allows attackers to potentially spoof user interface elements, making it appear as though legitimate applications are displaying different content or functionality than what is actually occurring. This UI spoofing capability could be particularly dangerous in contexts where users might be tricked into entering sensitive information or making decisions based on manipulated interface elements.
The operational impact of this vulnerability extends beyond simple visual deception to potentially enable more sophisticated attacks such as phishing or social engineering campaigns. When users encounter manipulated interface elements, they may be misled into trusting malicious content or actions that appear legitimate due to the compromised visual presentation. This vulnerability demonstrates the critical importance of proper state management in user interface components, as inconsistent UI behavior can erode user trust and create opportunities for more serious security breaches. The issue represents a failure in the principle of least privilege within the graphical user interface subsystem, where unauthorized manipulation of UI state could provide attackers with footholds for further exploitation.
Mitigation strategies for CVE-2018-4391 primarily focus on applying the vendor-provided security updates that address the underlying state management issues. System administrators should prioritize deployment of macOS High Sierra 10.13.1, Security Update 2017-001 for Sierra, Security Update 2017-004 for El Capitan, and the corresponding watchOS 4.3 and iOS 12.1 updates. Additionally, organizations should implement network monitoring to detect unusual text message patterns that might indicate exploitation attempts, though this approach has limitations given the nature of the vulnerability. Users should remain vigilant about unexpected interface behavior and avoid interacting with applications that display inconsistent UI elements, particularly when receiving unsolicited messages or communications from unknown sources. The fix implemented by Apple addresses the core issue through enhanced validation of text message processing and improved state management protocols that prevent unauthorized UI modifications during message handling operations.