CVE-2016-3885 in Android
Summary
by MITRE
debuggerd/debuggerd.cpp in Debuggerd in Android 5.0.x before 5.0.2, 5.1.x before 5.1.1, 6.x before 2016-09-01, and 7.0 before 2016-09-01 mishandles the interaction between PTRACE_ATTACH operations and thread exits, which allows attackers to gain privileges via a crafted application, aka internal bug 29555636.
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Analysis
by VulDB Data Team • 09/15/2022
The vulnerability described in CVE-2016-3885 resides within the debuggerd component of Android operating systems, specifically affecting versions 5.0.x before 5.0.2, 5.1.x before 5.1.1, 6.x before 2016-09-01, and 7.0 before 2016-09-01. This flaw exists in the debuggerd.cpp file and represents a critical privilege escalation vulnerability that stems from improper handling of ptrace operations during thread lifecycle management. The issue manifests when debuggerd attempts to attach to processes using PTRACE_ATTACH while those processes are in the midst of thread termination, creating a race condition that can be exploited by malicious applications.
The technical root cause of this vulnerability lies in the improper synchronization between ptrace attachment operations and thread exit handling within the debuggerd subsystem. When a process attempts to attach to another process using ptrace, the debuggerd component must properly manage the lifecycle of threads within the target process. However, in affected Android versions, the system fails to adequately handle scenarios where threads within a target process are in the process of exiting while an attachment operation is in progress. This race condition creates a window where attacker-controlled applications can manipulate the debuggerd behavior to escalate privileges, effectively bypassing the normal security boundaries that separate user applications from system-level operations.
The operational impact of this vulnerability is severe and directly affects the core security model of Android systems. An attacker with a crafted application can exploit this flaw to gain elevated privileges, potentially allowing them to execute arbitrary code with system-level permissions. This privilege escalation capability undermines fundamental Android security mechanisms including application sandboxing, SELinux policies, and the overall integrity of the operating system's permission model. The vulnerability is particularly dangerous because it operates at the kernel level through ptrace system calls, making it difficult to detect and prevent through traditional application-level security measures.
This vulnerability maps directly to CWE-362, which describes a race condition that allows concurrent processes to access shared resources in an unsafe manner. The flaw also aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation', and T1055, which covers 'Process Injection'. The attack vector involves leveraging the debuggerd service to perform ptrace operations that can be manipulated to gain unauthorized access to system resources. Organizations should prioritize patching affected Android versions to address this vulnerability, as it represents a fundamental weakness in the operating system's security architecture that could enable complete system compromise. The vulnerability demonstrates the critical importance of proper synchronization in kernel-level components and highlights the need for comprehensive security testing of system services that interact with process management operations.