CVE-2019-18786 in Linux
Summary
by MITRE
In the Linux kernel through 5.3.8, f->fmt.sdr.reserved is uninitialized in rcar_drif_g_fmt_sdr_cap in drivers/media/platform/rcar_drif.c, which could cause a memory disclosure problem.
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Analysis
by VulDB Data Team • 02/05/2024
The vulnerability identified as CVE-2019-18786 resides within the Linux kernel version 5.3.8 and earlier, specifically within the rcar_drif_g_fmt_sdr_cap function located in the drivers/media/platform/rcar_drif.c file. This issue represents a classic case of uninitialized memory access that can lead to information disclosure vulnerabilities. The flaw manifests when the f->fmt.sdr.reserved field remains uninitialized during the processing of SDR (Software Defined Radio) capture format operations, creating a potential vector for attackers to extract sensitive data from kernel memory regions.
The technical nature of this vulnerability aligns with CWE-457, which describes the use of uninitialized variables in software systems. In this context, the uninitialized f->fmt.sdr.reserved field creates a memory disclosure scenario where adjacent memory contents may be inadvertently exposed to userspace applications. The rcar_drif driver is responsible for handling media capture operations on Renesas R-Car SoC platforms, making this vulnerability particularly concerning for embedded systems and IoT devices running affected kernel versions. When the driver processes SDR capture format requests, the uninitialized memory field can contain leftover data from previous operations, potentially exposing kernel memory contents including sensitive information such as cryptographic keys, system pointers, or other confidential data.
From an operational perspective, this vulnerability could be exploited by malicious actors with local access to the system to perform information disclosure attacks. The attack vector requires a user-space process to interact with the media capture subsystem, specifically triggering the rcar_drif_g_fmt_sdr_cap function through appropriate ioctls. The impact extends beyond simple information leakage as the disclosed memory contents could contain system state information that might aid in further exploitation attempts. According to ATT&CK framework, this vulnerability maps to T1005 (Data from Local System) and T1059 (Command and Scripting Interpreter) where an attacker could use the disclosed information to refine subsequent attacks or establish persistence mechanisms.
The exploitation of this vulnerability typically requires an attacker to have some level of local access to the target system, as the memory disclosure occurs during legitimate driver operations. However, the potential for remote exploitation cannot be entirely ruled out if the driver is accessible through network interfaces or if the vulnerability exists in a broader context of privilege escalation. The vulnerability affects systems using Renesas R-Car SoC platforms where the rcar_drif driver is active, particularly impacting embedded systems, automotive infotainment systems, and industrial control devices that rely on these specific hardware platforms. Organizations should prioritize patching affected systems and monitoring for potential exploitation attempts, as the uninitialized memory disclosure could serve as a stepping stone for more sophisticated attacks targeting the underlying system architecture.
Mitigation strategies include applying the kernel patch that properly initializes the f->fmt.sdr.reserved field before use, which addresses the root cause of the vulnerability. System administrators should also implement monitoring for unusual driver behavior and memory access patterns that might indicate exploitation attempts. Additionally, restricting access to media capture interfaces and implementing proper privilege separation can reduce the attack surface. The vulnerability demonstrates the importance of proper memory initialization practices in kernel code and highlights the need for comprehensive security testing of device drivers, particularly those handling sensitive data processing operations in embedded environments.