CVE-2007-3757 in iPhone
Summary
by MITRE
Safari in Apple iPhone 1.1.1 allows remote user-assisted attackers to trick the iPhone user into making calls to arbitrary telephone numbers via a crafted "tel:" link that causes iPhone to display a different number than the number that will be dialed.
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Analysis
by VulDB Data Team • 11/02/2017
The vulnerability described in CVE-2007-3757 represents a significant user interface deception flaw in Apple's Safari browser implementation on the iPhone 1.1.1 operating system. This issue stems from how the mobile browser handles telephone number hyperlinks, specifically those formatted with the tel: URI scheme. The flaw operates through a sophisticated social engineering attack vector where malicious actors can craft deceptive telephone links that appear to dial one number while actually initiating calls to completely different telephone numbers. This type of vulnerability falls under the category of user interface deception and can be classified as CWE-693, which addresses protection mechanisms that are bypassed or circumvented by design. The attack requires user interaction and is categorized as user-assisted rather than purely remote, as the victim must actively click on the malicious link for the exploit to succeed.
The technical implementation of this vulnerability occurs at the application layer where Safari processes tel: URI schemes without proper validation or sanitization of the target telephone numbers. When a user encounters a crafted link, the browser displays a phone number that appears to be the intended recipient but executes a different number from the same link. This discrepancy creates a false sense of security for users who may believe they are calling a legitimate contact while actually executing commands that could result in unauthorized charges or privacy breaches. The vulnerability specifically impacts the iPhone 1.1.1 firmware version and represents a failure in input validation and output sanitization within the mobile browser's handling of telephone number protocols. The underlying mechanism operates through the phone application's interpretation of URI schemes, where the display interface and actual dialing mechanism are decoupled without proper verification.
The operational impact of this vulnerability extends beyond simple financial fraud to encompass broader security implications for mobile device users. Users may inadvertently incur charges for calls to premium rate numbers or international destinations that appear to be benign when viewing the link display. The vulnerability can be exploited in phishing campaigns where attackers craft links that appear to dial customer service numbers or emergency contacts, but instead redirect to expensive or malicious phone numbers. This type of attack aligns with ATT&CK technique T1566 which describes social engineering tactics used to manipulate users into performing actions that compromise security. The vulnerability also represents a failure in the principle of least privilege and input validation, as the system should ensure that displayed information matches the actual action performed. Organizations and individuals using mobile devices are particularly vulnerable as this attack vector can be easily propagated through email, text messages, or web content without requiring sophisticated technical skills from the attacker.
Mitigation strategies for CVE-2007-3757 should focus on both immediate user education and system-level protections. Users must be trained to verify telephone numbers before clicking on any tel: links, particularly those received through untrusted sources. The recommended approach involves implementing strict input validation at the application level where any telephone number URI is verified against a trusted source or sanitized before execution. System administrators should consider deploying mobile device management solutions that can block or warn users about potentially malicious telephone number links. The vulnerability highlights the importance of proper URI scheme handling and suggests implementing a verification mechanism that ensures the display information matches the actual action. Security patches should address the core issue by ensuring that the phone application properly validates telephone number URIs and prevents any discrepancy between the displayed number and the actual number that will be dialed. Organizations should also implement network-level controls that can detect and block malicious telephone number links, particularly those that redirect to premium rate or international numbers. This vulnerability demonstrates the critical need for comprehensive security testing of mobile applications, particularly those involving direct system interactions such as phone dialing functionality. The flaw also underscores the necessity of maintaining current firmware versions and implementing robust security awareness training programs to protect against social engineering attacks that exploit user trust in familiar interfaces.