CVE-2019-6223 in iOS
Summary
by MITRE
A logic issue existed in the handling of Group FaceTime calls. The issue was addressed with improved state management. This issue is fixed in iOS 12.1.4, macOS Mojave 10.14.3 Supplemental Update. The initiator of a Group FaceTime call may be able to cause the recipient to answer.
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Analysis
by VulDB Data Team • 01/29/2025
The vulnerability described in CVE-2019-6223 represents a significant security flaw in Apple's FaceTime implementation that exploited a logic error in group call handling mechanisms. This issue specifically affected the state management processes that govern how FaceTime calls transition between different operational phases, creating an unintended pathway for unauthorized call initiation. The flaw existed within the core Group FaceTime functionality where the system failed to properly validate the call initiation sequence, allowing malicious actors to manipulate the call flow in ways that were not intended by the application's design. The vulnerability was particularly concerning because it could be exploited by an attacker who controlled the call initiation process, potentially enabling them to force recipients to answer calls without their explicit consent.
The technical nature of this vulnerability stems from inadequate state validation within the FaceTime application's call management system. When a user initiated a Group FaceTime call, the application's internal state machine did not properly enforce the expected sequence of operations that should occur before a recipient could be prompted to answer. This logic flaw allowed an attacker to manipulate the call initiation process by exploiting the gap in state validation, effectively bypassing the normal user consent mechanisms. The issue was classified under CWE-284, which deals with improper access control, and specifically manifested as a weakness in the authorization process where the system failed to properly verify that the call initiation was legitimate and authorized. The vulnerability was particularly insidious because it did not require any special privileges or root access, making it exploitable through standard user interactions with the FaceTime application.
The operational impact of this vulnerability extended beyond simple privacy concerns to encompass potential security risks that could be leveraged for more sophisticated attacks. An attacker who successfully exploited this vulnerability could force any recipient to answer a FaceTime call, potentially leading to unwanted communication, privacy violations, or even social engineering attacks where the forced call could be used to gather information about the target. The vulnerability was particularly dangerous because it could be exploited remotely without requiring physical access to the device, and the attack could be executed through legitimate FaceTime functionality that users routinely trust and use. This created a scenario where users might unknowingly participate in calls that were initiated by attackers, potentially leading to information disclosure or other security incidents that could be difficult to trace back to the original exploit.
Apple addressed this vulnerability through a targeted fix that improved the state management protocols within the FaceTime application. The security update implemented enhanced validation checks that ensure proper call initiation sequences are followed before any recipient is prompted to answer a group call. The fix was included in iOS 12.1.4 and macOS Mojave 10.14.3 Supplemental Update, representing a critical security patch that restored proper authorization controls within the FaceTime system. Organizations and users should have immediately applied these updates to protect against exploitation of this vulnerability. The remediation approach aligns with the ATT&CK framework's mitigation strategies for privilege escalation and access control weaknesses, specifically addressing the technique of "Exploitation for Privilege Escalation" by ensuring that unauthorized call initiation cannot occur through manipulation of the application's state management. This vulnerability serves as a reminder of the importance of proper state validation in communication applications and the potential security implications when such validation is insufficient.