CVE-2017-13844 in macOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 11.1 is affected. The issue involves the "Messages" component. It allows physically proximate attackers to view arbitrary photos via a Reply With Message action in the lock-screen state.
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Analysis
by VulDB Data Team • 01/26/2021
The vulnerability identified as CVE-2017-13844 represents a significant security flaw within Apple's iOS messaging ecosystem that persisted through versions prior to iOS 11.1. This issue specifically targets the Messages application component and exploits a design weakness that allows unauthorized access to sensitive visual content. The vulnerability manifests when an attacker with physical proximity to a locked device can bypass the lock screen security mechanisms to access photos stored on the device through the Reply With Message functionality. This represents a critical failure in the device's access control model where the security boundary between the lock screen and application interfaces has been compromised.
The technical flaw resides in how the Messages application handles the Reply With Message action when the device is locked. When a user receives a message and chooses to reply with a photo, the system fails to properly enforce authentication checks that should prevent unauthorized access to the device's photo library. This weakness allows attackers to leverage the legitimate messaging functionality to gain access to arbitrary photos stored on the device. The vulnerability specifically affects the lock screen state where the system should enforce strict access controls, yet the Reply With Message action creates an unintended path for privilege escalation. The flaw demonstrates poor input validation and insufficient access control enforcement within the messaging framework, creating a bypass mechanism that undermines the fundamental security assumptions of the lock screen protection.
From an operational impact perspective, this vulnerability exposes users to significant privacy risks as it allows attackers with physical proximity to access sensitive personal photographs without requiring authentication. The attack vector is particularly concerning because it leverages legitimate device functionality rather than requiring sophisticated exploitation techniques or root access. An attacker can simply unlock the device, open the Messages app, select a conversation, and use the Reply With Message feature to access the photo library, effectively bypassing the lock screen security. This vulnerability directly impacts user privacy and data protection, as it enables unauthorized access to personal visual content that users expect to be protected by device-level security measures. The attack requires minimal technical expertise and can be executed by anyone with physical access to the target device, making it particularly dangerous in environments where device theft or unauthorized access might occur.
The vulnerability maps to CWE-284 Access Control Issues, specifically addressing insufficient access control mechanisms that allow unauthorized access to protected resources. This weakness falls under the broader category of privilege escalation vulnerabilities where a legitimate user action creates an unintended access path. The attack pattern aligns with ATT&CK technique T1056.001 Credential Access: Brute Force/Dictionary, though it operates through a different mechanism involving lock screen bypass rather than credential guessing. The security implications extend beyond simple photo access to encompass potential data exfiltration, identity theft, and privacy violations that could be exploited for malicious purposes. Organizations and individuals should consider this vulnerability as part of their broader mobile security posture, particularly in environments where physical security controls are inadequate. The remediation requires updating to iOS 11.1 or later versions where Apple has implemented proper access control enforcement for the Reply With Message functionality, ensuring that photo library access is properly restricted even when using legitimate messaging features. Additionally, users should be educated about the risks of leaving devices unlocked in public spaces and should implement additional security measures such as strong passcodes and automatic lock timeouts to minimize exposure to such attacks.