CVE-2016-1770 in Mac OS X
Summary
by MITRE
The Reminders component in Apple OS X before 10.11.4 allows attackers to bypass an intended user-confirmation requirement and trigger a dialing action via a tel: URL.
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Analysis
by VulDB Data Team • 11/12/2024
The vulnerability identified as CVE-2016-1770 resides within the Reminders application component of Apple's operating system, specifically affecting versions prior to macOS 10.11.4. This security flaw represents a critical oversight in the application's handling of universal resource identifiers, particularly those prefixed with the tel: scheme designed for telephone number dialing. The vulnerability manifests when the system processes malicious tel: URLs that could be embedded within reminder items, potentially enabling unauthorized phone calls to be initiated without explicit user consent.
The technical nature of this vulnerability stems from insufficient input validation and sanitization within the Reminders application's URL parsing mechanism. When a user encounters a reminder containing a tel: URL, the system fails to properly verify the legitimacy of the dialing action before executing it. This represents a clear violation of the principle of least privilege and user consent, as the application bypasses normal user confirmation prompts that should be required before initiating any phone call. The flaw operates at the application layer and exploits the trust relationship between the user and the system, allowing malicious actors to craft reminder items that automatically trigger telephone connections when opened or interacted with.
From an operational perspective, this vulnerability creates a significant attack surface that could be exploited by threat actors to perform unauthorized actions on affected systems. An attacker could potentially embed malicious tel: URLs within reminder items that appear legitimate to users, thereby tricking them into inadvertently triggering phone calls to premium-rate numbers or emergency services. The impact extends beyond simple inconvenience to potential financial loss and privacy violations, as users may unknowingly incur charges for unauthorized calls or have their personal information exposed through such actions. This vulnerability particularly affects environments where users may be less vigilant about the content of reminder items or where the Reminders application is used in shared or public computing environments.
The security implications of CVE-2016-1770 align with CWE-352, which addresses Cross-Site Request Forgery (CSRF) vulnerabilities, as the flaw enables unauthorized actions to be performed on behalf of users without their knowledge or consent. Additionally, this vulnerability maps to ATT&CK technique T1059.007, which covers "Command and Scripting Interpreter: JavaScript," as the exploitation may involve JavaScript-based URL handling within the Reminders application context. The vulnerability also demonstrates characteristics of privilege escalation through user interface manipulation, as it exploits the trust users place in seemingly benign reminder applications. Organizations should implement immediate mitigation strategies including updating to macOS 10.11.4 or later, reviewing existing reminder items for potentially malicious content, and educating users about the risks of interacting with untrusted reminder data. The remediation process should also include monitoring for unauthorized phone call activity that may indicate exploitation of this vulnerability, as well as implementing network-level controls to prevent connections to suspicious telephone numbers.