CVE-2015-5839

Vulnerability

dyld, the dynamic linker in Apple iOS before 9, fails to properly validate code signatures. An attacker can bypass the code-signing protection mechanism by placing a crafted signature in an executable file [1]. This affects all devices running iOS versions prior to 9.

Exploitation

An attacker needs the ability to install an app on an iOS device (via developer provisioning or physical access) and embed a specially crafted signature in one of the app's executable files. No additional network position or user interaction is required beyond installing the malicious app [1].

Impact

Successful exploitation allows the attacker to execute arbitrary unsigned code in the context of the app, effectively bypassing iOS code-signing enforcement. This undermines the platform's integrity and can lead to unauthorized code execution, potentially exfiltrating data or escalating privileges further [1].

Mitigation

Apple addressed this issue in iOS 9, released on September 16, 2015 [1]. Users should update their devices to iOS 9 or later. No workaround is available for earlier versions.