CVE-2007-3755 in iPhone
Summary
by MITRE
Mail in Apple iPhone 1.1.1 allows remote user-assisted attackers to force the iPhone user to make calls to arbitrary telephone numbers via a "tel:" link, which does not prompt the user before dialing the number.
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Analysis
by VulDB Data Team • 03/15/2021
The vulnerability described in CVE-2007-3755 represents a critical security flaw in the Apple iPhone 1.1.1 operating system that exposes users to unauthorized telephony operations. This issue affects the email client component of the iPhone's mobile operating system and demonstrates a fundamental failure in user consent mechanisms for critical system functions. The vulnerability specifically impacts the handling of telephone number links within email messages, creating a dangerous scenario where malicious actors can exploit this weakness to execute unauthorized calls without user confirmation. This flaw operates at the intersection of web-based content execution and mobile telephony functionality, presenting a unique attack surface that combines email-based delivery with immediate system action.
The technical implementation of this vulnerability stems from insufficient validation and user confirmation mechanisms within the iPhone's email client application. When a user receives an email containing a "tel:" URI scheme link, the system fails to present an explicit user interface prompt requesting confirmation before initiating the telephone call. This design flaw allows attackers to craft malicious emails that automatically trigger phone calls to predetermined numbers simply by clicking on embedded telephone links. The vulnerability essentially removes the user's ability to make an informed decision about whether to proceed with a call, bypassing the standard security protocols that should govern such sensitive operations. From a cybersecurity perspective, this represents a complete breakdown in the principle of least privilege and user consent, where the system automatically executes potentially harmful actions without proper authorization.
The operational impact of this vulnerability extends beyond simple unauthorized calling, as it creates potential for significant financial loss, privacy breaches, and social engineering attacks. Attackers can leverage this vulnerability to generate unexpected charges on victim's phone accounts by directing calls to premium-rate numbers, or to facilitate more sophisticated attacks such as social engineering campaigns where the automated calling functionality helps establish trust or creates distractions. The remote user-assisted nature of this attack means that victims do not need to directly interact with malicious content to be compromised, as simply opening an email containing the malicious link can trigger the unwanted behavior. This vulnerability particularly affects the mobile security model of the time, where the assumption was that email content would not automatically execute system-level operations without explicit user interaction.
Security professionals should note that this vulnerability aligns with several established threat patterns and attack vectors documented in cybersecurity frameworks, particularly those related to client-side exploitation and phishing attacks. The flaw demonstrates characteristics consistent with CWE-601 URL Redirector Abuse, where web-based content can redirect users to unintended system actions without proper validation. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and execution through social engineering, as it exploits user trust in email applications to achieve unauthorized system access. The vulnerability also reflects broader concerns about mobile application security and the need for comprehensive input validation across all application components that interact with system-level functions. Organizations should consider this vulnerability as representative of the critical importance of user interface security controls and the necessity of implementing explicit confirmation mechanisms for any operation that could result in financial loss or privacy exposure.
Mitigation strategies for this vulnerability require both immediate patching and operational security improvements. Apple's subsequent release of security updates addressed this specific flaw by implementing mandatory user confirmation prompts for all telephone number links, demonstrating the importance of rapid response to critical security issues. Organizations should ensure that all mobile devices receive timely security updates and implement email filtering mechanisms that can identify and quarantine potentially malicious content containing telephone link schemes. Additionally, user education programs should emphasize the dangers of clicking on unknown telephone links in email messages, as the vulnerability primarily exploits user behavior rather than technical system weaknesses. The incident highlights the need for comprehensive security testing of mobile applications, particularly focusing on user interaction flows and the automatic execution of system functions based on external input sources.