CVE-2016-4486 in Linux
Summary
by MITRE
The rtnl_fill_link_ifmap function in net/core/rtnetlink.c in the Linux kernel before 4.5.5 does not initialize a certain data structure, which allows local users to obtain sensitive information from kernel stack memory by reading a Netlink message.
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Analysis
by VulDB Data Team • 11/09/2024
The vulnerability identified as CVE-2016-4486 represents a classic information disclosure flaw within the Linux kernel's networking subsystem. This issue resides in the rtnl_fill_link_ifmap function located in the net/core/rtnetlink.c file, affecting Linux kernel versions prior to 4.5.5. The vulnerability stems from improper initialization of a data structure during the processing of Netlink messages, creating a pathway for unauthorized information extraction from kernel memory space.
The technical implementation of this vulnerability involves the rtnl_fill_link_ifmap function failing to properly initialize specific kernel data structures before populating them with information. When local users send crafted Netlink messages to the kernel, the uninitialized memory regions contain residual data from previous operations or kernel stack contents. This uninitialized data becomes accessible through the Netlink response messages, allowing attackers to potentially extract sensitive information including kernel pointers, stack contents, or other confidential data that may have been previously stored in those memory locations. The flaw specifically impacts the kernel's routing netlink interface which handles network interface configuration and status information.
The operational impact of this vulnerability extends beyond simple information disclosure, as the leaked kernel memory could contain sensitive data such as cryptographic keys, memory addresses, or other confidential information that might aid in subsequent exploitation attempts. Local attackers with minimal privileges can leverage this vulnerability to gain insights into kernel memory layout and internal state, potentially enabling more sophisticated attacks including privilege escalation or bypassing security mechanisms. The vulnerability's classification aligns with CWE-1280 which addresses information exposure through improper initialization and CWE-200 which covers exposure of sensitive information.
This vulnerability relates to the broader ATT&CK framework category of privilege escalation and information gathering, where adversaries can use information disclosure to better understand system internals and identify potential attack vectors. The issue demonstrates the critical importance of proper memory initialization in kernel space, as uninitialized memory can contain remnants of previous operations that should not be accessible to user-space processes. The vulnerability highlights the need for comprehensive security testing of kernel components, particularly those handling network communication and data structures that interface with user-space applications.
Mitigation strategies for CVE-2016-4486 involve applying the official kernel patch released with version 4.5.5, which properly initializes the affected data structures before processing Netlink messages. System administrators should prioritize updating kernel versions across all affected systems, particularly those running older kernel versions where this vulnerability remains unpatched. Additional protective measures include implementing proper access controls to limit local user privileges, monitoring for unusual Netlink message patterns, and maintaining comprehensive system logging to detect potential exploitation attempts. The vulnerability serves as a reminder of the critical security implications of seemingly minor initialization errors in kernel code, emphasizing the need for rigorous code review processes and security testing of kernel subsystems that handle sensitive data processing.