CVE-2015-5839 in Watch
Summary
by MITRE
dyld in Apple iOS before 9 allows attackers to bypass a code-signing protection mechanism via an app that places a crafted signature in an executable file.
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Analysis
by VulDB Data Team • 11/21/2024
The vulnerability identified as CVE-2015-5839 resides within Apple's dynamic link editor dyld component that operates within iOS versions prior to 9.0. This flaw represents a critical code-signing bypass that undermines the fundamental security architecture designed to ensure only trusted applications can execute on iOS devices. The vulnerability specifically targets the code-signing verification process that Apple implements to validate the integrity and authenticity of applications before execution. When an application is installed on iOS, the system checks the digital signature embedded within the application bundle to confirm it originates from a trusted source and has not been tampered with during distribution.
The technical implementation of this vulnerability exploits a flaw in how dyld processes executable files containing crafted signatures. Attackers can manipulate the structure of executable files to place maliciously crafted signature data in locations where the code-signing verification mechanism will not properly validate the signature. This allows malicious code to be executed while appearing to have valid code-signing credentials, effectively circumventing the security controls that prevent unauthorized applications from running on iOS devices. The flaw essentially creates a bypass mechanism that enables attackers to inject malicious code into applications that would otherwise be rejected by the system's code-signing enforcement.
The operational impact of this vulnerability extends far beyond simple code execution bypass. It represents a significant threat to iOS device security as it allows attackers to run malicious applications without proper code-signing verification, potentially enabling the execution of malware, rootkit installations, or other malicious payloads. The vulnerability affects all iOS versions prior to 9.0, creating a substantial attack surface across a wide range of devices. This flaw particularly undermines the security model that Apple has built into iOS, which relies heavily on code-signing as a primary defense mechanism against unauthorized software execution. The vulnerability is particularly concerning because it operates at the system level where it can bypass security controls that are fundamental to iOS's security architecture.
From a cybersecurity perspective, this vulnerability aligns with CWE-257, which addresses insecure storage of credentials and code-signing information, and can be categorized under ATT&CK technique T1059 for execution through code injection. The attack vector specifically targets the code-signing verification process, which is part of the broader category of system integrity protection mechanisms. Organizations and security professionals should note that this vulnerability represents a significant risk to iOS device security and requires immediate remediation through iOS updates. The exploitability of this vulnerability demonstrates the importance of maintaining up-to-date security patches and highlights the critical nature of code-signing mechanisms in mobile operating systems. The vulnerability also underscores the need for comprehensive security testing of system-level components and the importance of robust code-signing validation processes in preventing unauthorized code execution.
The mitigation strategy for this vulnerability requires immediate deployment of iOS 9.0 or later updates, which contain patches addressing the code-signing bypass mechanism. Security administrators should ensure all iOS devices within their environment are updated to versions that include the necessary security fixes. Additionally, organizations should implement monitoring for suspicious application installations and maintain awareness of potential exploitation attempts targeting this vulnerability. The fix implemented by Apple addresses the root cause of the issue by strengthening the code-signing verification process and ensuring that signature validation occurs properly regardless of the signature placement within executable files. This vulnerability serves as a reminder of the critical importance of maintaining secure code-signing practices and the potential consequences when these mechanisms are compromised.