CVE-2013-5155 in iOS
Summary
by MITRE
The Sandbox subsystem in Apple iOS before 7 allows attackers to cause a denial of service (infinite loop) via an application that writes crafted values to /dev/random.
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Analysis
by VulDB Data Team • 05/25/2021
The vulnerability identified as CVE-2013-5155 represents a critical flaw in Apple iOS sandboxing mechanisms that existed prior to version 7. This issue resides within the kernel-level sandbox subsystem responsible for isolating applications and preventing unauthorized access to system resources. The vulnerability specifically targets the interaction between applications and the /dev/random device file, which serves as the primary interface for accessing cryptographically secure random number generation within the operating system. The sandbox subsystem's failure to properly validate or sanitize input values written to this device creates a pathway for malicious applications to manipulate the system's random number generator behavior. This flaw demonstrates a fundamental weakness in the kernel's input validation processes and highlights the importance of proper resource management within privileged system components.
The technical exploitation of this vulnerability occurs when an application attempts to write specifically crafted values to the /dev/random device file. These crafted values trigger an infinite loop within the kernel's random number generation algorithm, causing the system to become unresponsive or enter a state where it cannot process further requests. The flaw essentially creates a condition where the system's random number generator becomes trapped in a continuous loop, consuming system resources and effectively causing a denial of service condition that impacts the entire operating system's functionality. This type of vulnerability falls under CWE-691, which specifically addresses insufficient control of a resource through a potentially vulnerable input, and represents a classic example of a resource exhaustion attack that leverages kernel-level components. The infinite loop mechanism operates at the kernel level, bypassing normal application sandboxing controls and directly impacting system stability.
The operational impact of CVE-2013-5155 extends beyond simple denial of service conditions to potentially compromise the entire iOS ecosystem's security model. When an attacker successfully exploits this vulnerability, they can effectively lock up the device or cause system-wide instability, rendering the device unusable until a reboot occurs. This vulnerability undermines the core security principle of application isolation that iOS relies upon, as it allows a single compromised application to affect system-level operations. The attack vector demonstrates how improper validation of device file access can create a pathway for privilege escalation or system-wide compromise, as the infinite loop condition prevents normal system operations from completing. This type of vulnerability is particularly concerning because it operates below the application layer and can affect even system-level processes that depend on random number generation for security functions such as cryptographic key generation, session management, and secure communications.
Mitigation strategies for CVE-2013-5155 primarily involve upgrading to iOS version 7 or later, which includes kernel-level patches that properly validate input values written to the /dev/random device. Apple's patch addresses the vulnerability by implementing stricter input validation and bounds checking within the random number generation subsystem, preventing malicious values from triggering the infinite loop condition. Organizations should also implement monitoring solutions that can detect anomalous behavior patterns related to device file access and random number generation. The vulnerability highlights the importance of proper kernel security practices and demonstrates how seemingly simple device file operations can become critical security concerns when proper validation is absent. From an ATT&CK framework perspective, this vulnerability maps to technique T1499.004 which covers Network Denial of Service, and T1068 which addresses Exploitation for Privilege Escalation, as the flaw can potentially be leveraged to gain elevated privileges through system instability. Additionally, this vulnerability underscores the necessity of proper input sanitization and the principle of least privilege in kernel-level operations, as recommended by various security frameworks including NIST SP 800-53 and ISO 27001 standards.