Description

A severe vulnerability has been discovered in Apple's iOS activation infrastructure, specifically impacting the backend endpoint https://humb.apple.com/humbug/baa. This flaw enables attackers to inject unauthorized XML .plist payloads during device pre-activation or user setup stages by spoofing authentication. As of testing with iOS 18.5 in May 2025, this vulnerability allows for arbitrary device provisioning, persistent configuration alterations, and the bypass of Mobile Device Management (MDM) controls, which can occur without requiring a jailbreak or physical access to the device. The core issue lies in the backend's failure to validate signatures and authenticity of these payloads, making it susceptible to XML External Entity (XXE) Injection Attacks and the covert insertion of malicious configurations. This critical vulnerability can be exploited through various means, such as captive portals, rogue access points, or even supply chain interferences, creating opportunities for post-configuration tampering. The backend's response with a 200 OK status to even malformed payloads is a significant concern, as it allows attackers to silently implant background tasks, modify modem policies, and introduce unauthorized profiles without detection. Forensic evidence from sysdiagnose logs on freshly reset devices points to pre-activation compromising configuration drift, which is supported by unmonitored configuration entries and the trim claim. A notable instance, dubbed "SignalGate," demonstrated how secure messaging functionality could be compromised without any visible indicators on the user interface. To mitigate the immediate risks, Apple users and enterprise IT departments should refrain from initializing or activating devices on unsecured or untrusted networks until Apple releases an official patch. Implementing robust early anomaly detection during the device onboarding process is also crucial. This vulnerability underscores the urgent need for stricter validation protocols during iOS device activation, particularly in sensitive or regulated environments where secure provisioning is non-negotiable.