CVE-2016-1763 in iOS
Summary
by MITRE
Messages in Apple iOS before 9.3 does not ensure that an auto-fill action applies to the intended message thread, which allows remote authenticated users to obtain sensitive information by providing a crafted sms: URL and reading a thread.
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Analysis
by VulDB Data Team • 07/11/2022
The vulnerability described in CVE-2016-1763 represents a critical information disclosure flaw within Apple iOS versions prior to 9.3. This security weakness resides in the mobile operating system's handling of auto-fill functionality for messaging applications, specifically affecting how the system processes sms: URLs. The vulnerability enables malicious actors to exploit a design flaw in the message thread association mechanism, allowing them to access sensitive data from unintended conversation threads. The flaw stems from insufficient validation of message context when auto-fill actions are triggered through specially crafted sms: URLs, creating a pathway for unauthorized information retrieval.
The technical implementation of this vulnerability involves the improper handling of URL schemes within the iOS messaging framework. When a user encounters a crafted sms: URL, the system's auto-fill mechanism fails to properly verify that the action applies to the intended message thread. This allows an attacker to manipulate the context in which auto-fill operations occur, potentially accessing messages from different conversations. The vulnerability specifically affects the relationship between URL parsing and message thread management, where the system does not adequately validate the target thread context before executing auto-fill operations. This issue falls under the category of insufficient input validation and improper privilege management as defined by CWE-20 and CWE-269.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially compromise user privacy and communications security. Remote authenticated users can exploit this flaw to access sensitive information from other message threads without proper authorization, creating a significant risk for personal and potentially business communications. The vulnerability is particularly concerning because it operates through legitimate URL handling mechanisms that users encounter during normal messaging operations, making detection difficult and exploitation relatively straightforward. Attackers can craft malicious sms: URLs that, when clicked, trigger auto-fill actions that retrieve messages from unintended conversations, potentially accessing personal information, credentials, or confidential communications.
From a cybersecurity perspective, this vulnerability aligns with several ATT&CK framework techniques including T1566 for spearphishing with links and T1005 for data from local systems. The flaw demonstrates a classic example of how seemingly benign URL handling can create security risks when proper context validation is missing from the implementation. Organizations should consider this vulnerability as part of broader mobile security assessments, particularly in environments where iOS devices handle sensitive information. The vulnerability also highlights the importance of proper input validation and context awareness in mobile application development, as the flaw exists in the core messaging infrastructure rather than in specific applications. Remediation efforts should focus on implementing proper URL context validation and ensuring that auto-fill operations maintain strict thread boundaries to prevent unauthorized access to conversation data.
This vulnerability serves as a reminder of the critical importance of proper context validation in mobile operating systems and the potential for seemingly minor implementation flaws to create significant security risks. The lack of proper thread validation in the auto-fill mechanism represents a fundamental security gap that could be exploited in various attack scenarios, including targeted information gathering and privacy violations. Users should be advised to update to iOS 9.3 or later versions where this vulnerability has been addressed through improved input validation and context management within the messaging system.