CVE-2015-3715 in Mac OS X
Summary
by MITRE
The code-signing implementation in Apple OS X before 10.10.4 does not properly consider libraries that are external to an application bundle, which allows attackers to bypass intended launch restrictions via a crafted library.
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Analysis
by VulDB Data Team • 11/25/2024
The vulnerability identified as CVE-2015-3715 represents a critical code-signing flaw within Apple's macOS operating system affecting versions prior to 10.10.4. This security weakness resides in the code-signing implementation that governs how applications and their dependencies are validated before execution. The flaw specifically manifests when the system fails to properly verify external libraries that exist outside of an application bundle, creating a potential vector for privilege escalation and unauthorized code execution. The vulnerability operates at the intersection of application sandboxing and code integrity mechanisms, where the operating system's trust model becomes compromised due to insufficient validation of dynamically linked libraries.
The technical implementation of this vulnerability stems from the improper handling of library loading within the macOS code-signing framework. When an application attempts to load external libraries, the system should validate these components against the application's code-signing certificate and entitlements. However, in affected versions, the code-signing verification process does not adequately examine libraries that are not contained within the application bundle's designated directory structure. This oversight allows malicious actors to craft specially designed libraries that can be loaded by legitimate applications, effectively bypassing the intended launch restrictions and security boundaries that code-signing is meant to enforce. The vulnerability can be categorized under CWE-315 which deals with cleartext storage of sensitive information in a manner that allows unauthorized access, though in this case it relates more specifically to improper validation of external dependencies.
The operational impact of CVE-2015-3715 extends beyond simple code execution, as it fundamentally undermines the security model of macOS applications. Attackers can exploit this vulnerability to bypass application sandboxing controls, potentially gaining access to restricted system resources or user data. The flaw enables privilege escalation scenarios where malicious code can execute with elevated privileges, particularly when the compromised application has elevated entitlements. This vulnerability is particularly concerning in enterprise environments where macOS systems may be running older versions of the operating system, creating persistent attack vectors that can be leveraged for lateral movement or data exfiltration. The ATT&CK framework categorizes this type of vulnerability under T1546.003 which involves the use of code signing certificates for persistence, though the specific technique here focuses on bypassing code-signing validation rather than using legitimate certificates for malicious purposes.
Mitigation strategies for CVE-2015-3715 primarily center around updating to macOS version 10.10.4 or later, which contains the patched code-signing implementation. System administrators should prioritize deployment of this security update across all affected macOS systems, particularly those running in enterprise environments where the risk of exploitation is higher. Additional protective measures include implementing application whitelisting policies, monitoring for unauthorized library loading patterns, and ensuring that automatic updates are enabled on all systems. Organizations should also conduct vulnerability assessments to identify applications that may be susceptible to this type of exploitation and consider implementing additional security controls such as kernel extensions restrictions or more stringent library loading policies. The remediation process should include comprehensive testing to ensure that legitimate applications continue to function properly after the update, as code-signing changes can sometimes impact compatibility with existing software deployments.