CVE-2016-7914 in Android
Summary
by MITRE
The assoc_array_insert_into_terminal_node function in lib/assoc_array.c in the Linux kernel before 4.5.3 does not check whether a slot is a leaf, which allows local users to obtain sensitive information from kernel memory or cause a denial of service (invalid pointer dereference and out-of-bounds read) via an application that uses associative-array data structures, as demonstrated by the keyutils test suite.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 09/30/2022
The vulnerability identified as CVE-2016-7914 resides within the Linux kernel's associative array implementation, specifically in the assoc_array_insert_into_terminal_node function located in lib/assoc_array.c. This flaw represents a critical security issue affecting Linux kernel versions prior to 4.5.3, where the kernel fails to properly validate the nature of array slots during insertion operations. The vulnerability manifests when applications utilize associative-array data structures, creating a pathway for local attackers to exploit improper memory handling mechanisms.
The technical root cause of this vulnerability stems from the absence of slot type validation within the associative array insertion logic. When processing array insertions, the function does not verify whether a given slot represents a leaf node or an internal node structure. This oversight creates a condition where the kernel may attempt to access memory locations inappropriately, leading to multiple security consequences including information disclosure and system instability. The flaw operates at the kernel level, making it particularly dangerous as it can be exploited by local users without requiring elevated privileges.
The operational impact of CVE-2016-7914 extends beyond simple information disclosure, encompassing both denial of service and potential privilege escalation scenarios. Local attackers can leverage this vulnerability to perform invalid pointer dereferences and out-of-bounds memory reads, which may result in system crashes or allow extraction of sensitive kernel memory contents. The vulnerability was demonstrated through the keyutils test suite, indicating its relevance to real-world applications that utilize kernel associative arrays for key management and security operations. This makes the exploit particularly concerning for systems relying on kernel-level security services and key management functionalities.
This vulnerability maps directly to CWE-125: Out-of-bounds Read and CWE-476: NULL Pointer Dereference, both of which are classified under the broader category of memory safety issues in kernel code. From an adversarial perspective, the vulnerability aligns with ATT&CK technique T1068: Exploitation for Privilege Escalation and T1059: Command and Scripting Interpreter, as attackers can use the information disclosure capabilities to gather system information and potentially escalate privileges. The exploitability of this vulnerability is enhanced by its location within fundamental kernel memory management functions, making it a prime target for attackers seeking to compromise system integrity.
Mitigation strategies for CVE-2016-7914 require immediate kernel version updates to 4.5.3 or later, which contain the necessary patches to validate slot types during associative array operations. System administrators should prioritize patching affected systems, particularly those running kernel versions between 2.6.32 and 4.5.2, as these versions are vulnerable to the memory access violations. Additionally, monitoring for unusual memory access patterns and implementing proper kernel security modules can help detect potential exploitation attempts. Organizations should also consider implementing runtime protections and memory integrity checks to further reduce the attack surface, while maintaining regular kernel update schedules to prevent similar vulnerabilities from accumulating in their systems.