CVE-2018-4387 in iOS
Summary
by MITRE
A lock screen issue allowed access to photos via Reply With Message on a locked device. This issue was addressed with improved state management. This issue affected versions prior to iOS 12.1.
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Analysis
by VulDB Data Team • 04/08/2020
The vulnerability described in CVE-2018-4387 represents a critical security flaw in Apple's iOS operating system that compromised the device's lock screen protection mechanisms. This issue specifically affected devices running iOS versions prior to 12.1, creating a significant bypass in the system's security architecture that allowed unauthorized access to sensitive user data. The flaw manifested through the Reply With Message functionality, which is typically designed as a convenient communication tool but was exploited to gain access to photo content on locked devices. This represents a fundamental failure in the operating system's state management and access control implementation, where the security boundaries between locked and unlocked states were inadequately enforced.
The technical nature of this vulnerability aligns with CWE-284, which addresses improper access control issues, and demonstrates how insufficient state management can create security loopholes in mobile operating systems. The flaw exploited the device's inability to properly maintain its locked state when specific messaging functions were invoked, allowing attackers to navigate through the user interface and access photo libraries without proper authentication. This type of vulnerability falls under the ATT&CK technique T1546.001, which covers changes to system binaries and configuration files, as it involved manipulation of the device's security state management. The vulnerability was particularly concerning because it leveraged legitimate system functionality to bypass security measures, making it difficult to detect through conventional security monitoring approaches.
The operational impact of this vulnerability was substantial as it provided unauthorized access to personal photographs and potentially sensitive visual data stored on iOS devices. Users who were unaware of this vulnerability could have had their private photo collections accessed by anyone with physical access to their locked device, particularly during the time when the device was in use for messaging functions. The issue represented a failure in the principle of least privilege, where the system allowed access to resources beyond what was appropriate for the current security context. This vulnerability was especially problematic in environments where physical security was compromised or where devices might be left unattended, as it created an attack vector that required minimal technical expertise to exploit. The security implications extended beyond just photo access, as it demonstrated a broader weakness in how the operating system managed state transitions and access controls during active user sessions.
Apple addressed this vulnerability through improved state management mechanisms that properly enforced the security boundaries between locked and unlocked device states. The fix involved updating the operating system's handling of messaging functions to ensure that when a device was locked, access to photo libraries and other sensitive data would remain properly restricted regardless of which system functions were being invoked. This type of fix represents a classic example of implementing proper access control mechanisms and maintaining consistent security contexts throughout system operations. The remediation approach aligns with industry best practices for mobile security and demonstrates the importance of comprehensive state management in preventing privilege escalation attacks. Users were advised to update to iOS 12.1 or later versions to receive the necessary security patches that addressed this specific vulnerability and restored proper lock screen protection mechanisms.