A significant security flaw has been identified within Apple’s iOS activation infrastructure, allowing attackers to inject unauthenticated XML payloads during the device setup process. This vulnerability, present in the latest iOS 18.5 stable release as of May 2025, potentially exposes millions of Apple devices to pre-activation tampering and persistent configuration manipulation without requiring authentication or signature verification.
Understanding the Vulnerability
The core of this issue lies in Apple’s internal activation endpoint at `https://humb.apple.com/humbug/baa`, which processes device provisioning requests during initial setup. Attackers can exploit this weakness by sending malformed XML property list (`.plist`) payloads that the server accepts and processes without proper validation. This oversight creates opportunities for unauthorized configuration changes that persist beyond the activation phase.
Technical Mechanism of the Attack
The vulnerability stems from the activation server’s XML parsing implementation, which lacks essential security controls typically required for processing external data. When a device initiates the activation process, it communicates with Apple’s backend through XML-formatted requests containing device identifiers and provisioning information. Due to the server’s acceptance of unsigned payloads, attackers can craft malicious XML documents that modify device configurations during activation.
These payloads can include Document Type Definition (DOCTYPE) declarations, potentially enabling XML External Entity (XXE) attacks or other XML-based exploitation techniques. The absence of signature verification means the server cannot distinguish between legitimate Apple-generated provisioning data and attacker-controlled content. This vulnerability is particularly concerning for enterprise deployments where device provisioning policies are critical for security compliance.
Discovery and Analysis
Security analysts identified this vulnerability through extensive testing of the iOS activation backend. Their research revealed that the server’s tolerance for malformed content and support for DOCTYPE declarations create multiple attack vectors. The activation infrastructure’s lack of sender verification mechanisms allows arbitrary provisioning modifications to occur silently, with no error feedback provided to either the device or Apple’s monitoring systems.
Potential Impact
The discovery of this vulnerability highlights significant gaps in Apple’s backend security validation processes, potentially affecting the integrity of device configurations across the entire iOS ecosystem. Attackers exploiting this flaw could perform unauthorized configuration changes during device activation, leading to persistent security risks. This issue underscores the importance of robust validation mechanisms in critical infrastructure components to prevent such vulnerabilities.
Recommendations
To mitigate the risks associated with this vulnerability, it is recommended that Apple implement stringent validation and authentication mechanisms within the activation infrastructure. Ensuring that all incoming provisioning requests are properly authenticated and signed can prevent unauthorized modifications during the device setup process. Additionally, regular security audits and updates to the activation server’s XML parsing implementation can help identify and address potential vulnerabilities proactively.
