CVE-2016-1880 in FreeBSD
Summary
by MITRE
The Linux compatibility layer in the kernel in FreeBSD 9.3, 10.1, and 10.2 allows local users to read portions of kernel memory and potentially gain privilege via unspecified vectors, related to "handling of Linux futex robust lists."
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Analysis
by VulDB Data Team • 07/03/2022
The vulnerability identified as CVE-2016-1880 resides within the Linux compatibility layer of FreeBSD kernel versions 9.3, 10.1, and 10.2, representing a significant security weakness that enables local attackers to access kernel memory contents. This flaw specifically manifests in the handling of Linux futex robust lists, which are synchronization primitives used to manage thread locks and ensure proper resource management in multi-threaded applications. The issue stems from inadequate memory management within the compatibility layer that translates Linux system calls into FreeBSD equivalents, creating potential information disclosure pathways that could be exploited by malicious users with local access to the system. The vulnerability operates at the intersection of kernel-level memory management and userspace compatibility interfaces, making it particularly dangerous as it leverages the legitimate functionality of the Linux compatibility subsystem to achieve unauthorized memory access.
The technical implementation of this vulnerability involves the improper handling of robust futex lists during the Linux compatibility layer's processing of synchronization operations. Futexes, or fast userspace mutexes, are fundamental synchronization primitives that require careful memory management to prevent race conditions and ensure proper thread coordination. When FreeBSD's kernel processes Linux futex robust lists, it fails to properly validate or sanitize memory access patterns, allowing local users to potentially read kernel memory addresses and contents through crafted system calls. This memory disclosure capability can expose sensitive kernel data structures, including pointers to kernel functions, memory layout information, and other confidential data that could be instrumental in developing more sophisticated attacks. The vulnerability's classification aligns with CWE-200, which addresses improper information exposure, and represents a direct violation of memory safety principles in kernel space operations. The attack vector requires local system access but can be particularly dangerous when combined with other exploitation techniques that rely on information disclosure for privilege escalation.
The operational impact of CVE-2016-1880 extends beyond simple information disclosure, as the ability to read kernel memory can provide attackers with critical insights into system internals that may facilitate privilege escalation attacks. Local users who exploit this vulnerability can potentially gather information about kernel memory layout, function addresses, and other sensitive data that could be used to bypass security mechanisms or craft more targeted attacks. The vulnerability affects systems running FreeBSD versions 9.3, 10.1, and 10.2, which were widely deployed in enterprise and server environments, making the potential impact substantial across various operational contexts. The implications are particularly severe for systems that rely heavily on Linux compatibility features, as the vulnerability exists within core kernel functionality that handles legitimate cross-platform operations. This flaw can be exploited as part of a broader attack chain where the initial memory disclosure provides the foundation for more advanced exploitation techniques, potentially allowing attackers to gain elevated privileges and establish persistent access to compromised systems.
Mitigation strategies for CVE-2016-1880 focus primarily on updating affected FreeBSD systems to versions that contain patches addressing the memory handling issues within the Linux compatibility layer. System administrators should prioritize upgrading to FreeBSD versions 10.3 or later, which include fixes that properly validate memory access during futex robust list processing and prevent unauthorized kernel memory reads. The patch implementation addresses the root cause by introducing proper bounds checking and memory validation mechanisms that ensure only legitimate memory regions are accessed during Linux compatibility operations. Organizations should also consider implementing additional security controls such as mandatory access controls, kernel hardening configurations, and monitoring for suspicious system call patterns that might indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and credential access, specifically leveraging the T1068 privilege escalation technique through kernel memory disclosure. The mitigation approach aligns with defensive strategies outlined in the MITRE ATT&CK framework for preventing kernel-level exploits and maintaining system integrity through timely patch management and operational security measures.