CVE-2015-3756 in iOS
Summary
by MITRE
The Certificate UI in Apple iOS before 8.4.1 does not prevent X.509 certificate acceptance within the lock screen, which allows physically proximate attackers to establish arbitrary certificate trust relationships by completing a dialog.
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Analysis
by VulDB Data Team • 10/14/2017
The vulnerability identified as CVE-2015-3756 represents a significant security flaw in Apple iOS certificate handling mechanisms prior to version 8.4.1. This issue resides within the Certificate UI component of the operating system, specifically affecting how certificates are managed and accepted during the lock screen interaction process. The flaw fundamentally undermines the trust model that iOS employs to secure certificate installations, creating a pathway for malicious actors to bypass normal security controls through physical proximity alone. The vulnerability is classified under CWE-284, which deals with improper access control, and aligns with ATT&CK technique T1552.001 for credentials from password stores, as it enables unauthorized certificate trust establishment.
The technical implementation of this vulnerability stems from insufficient validation controls within the lock screen certificate acceptance process. When users encounter certificate dialogs while the device is locked, the system fails to properly enforce security boundaries that would normally prevent arbitrary certificate installation. Attackers exploiting this weakness can simply present a certificate to a locked device and complete the acceptance dialog, thereby establishing trust relationships that would normally require explicit user authentication and authorization. This represents a critical breakdown in the principle of least privilege and proper access control enforcement, as the system does not adequately verify the legitimacy of certificate installation requests during lock screen interactions.
The operational impact of CVE-2015-3756 extends beyond simple certificate acceptance, potentially enabling sophisticated attack scenarios including man-in-the-middle attacks, credential harvesting, and unauthorized system access. An attacker with physical access to a locked iOS device can establish trust for malicious certificates, allowing them to intercept encrypted communications, impersonate legitimate services, or gain elevated privileges within the system. The vulnerability is particularly dangerous in environments where mobile devices contain sensitive corporate or personal data, as it provides a direct pathway for attackers to compromise certificate-based security controls that are fundamental to secure communications. This flaw essentially transforms the lock screen from a security boundary into a potential attack vector.
Mitigation strategies for this vulnerability require immediate system updates to iOS version 8.4.1 or later, which implements proper lock screen certificate validation controls. Organizations should also implement comprehensive device management policies that enforce automatic updates and monitor for unauthorized certificate installations. Security teams should conduct regular vulnerability assessments focusing on certificate trust management and implement network monitoring to detect suspicious certificate-related activities. The remediation process should include comprehensive testing of certificate trust relationships and verification that proper access controls are enforced during lock screen interactions. Additionally, user awareness training should emphasize the importance of secure device handling and the risks associated with physical proximity attacks, as this vulnerability specifically exploits the gap between user expectations of lock screen security and the actual implementation of certificate acceptance controls.