CVE-2019-3846 in Linux
Summary
by MITRE • 01/25/2023
A flaw that allowed an attacker to corrupt memory and possibly escalate privileges was found in the mwifiex kernel module while connecting to a malicious wireless network.
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Analysis
by VulDB Data Team • 10/15/2024
The vulnerability identified as CVE-2019-3846 represents a critical memory corruption flaw within the mwifiex kernel module, which is responsible for managing Marvell wireless network adapters in Linux systems. This issue arises during the wireless network connection process when the kernel module fails to properly validate input data from malicious wireless networks. The flaw exists in the wireless driver's handling of beacon frames and association responses, creating opportunities for attackers to manipulate memory structures through specially crafted wireless network packets. The vulnerability is particularly concerning because it operates at the kernel level, where memory corruption can lead to arbitrary code execution and privilege escalation. According to CWE-121, this vulnerability falls under the category of stack-based buffer overflow conditions, while also aligning with CWE-125, which addresses out-of-bounds read errors that can occur when processing malformed network data. The ATT&CK framework categorizes this as a privilege escalation technique through kernel exploits, specifically targeting the kernel module execution environment where the wireless driver operates with elevated privileges.
The technical implementation of this vulnerability occurs when the mwifiex driver processes malformed wireless network frames that contain oversized or malformed fields in the beacon or association response packets. During normal wireless connection procedures, the driver allocates memory buffers to store information from these network frames, but fails to properly validate the length parameters before copying data into these buffers. When an attacker constructs malicious wireless networks with oversized fields or malformed data structures, the driver's memory management routines can be tricked into writing beyond allocated buffer boundaries. This memory corruption can overwrite critical kernel data structures, function pointers, or return addresses, potentially allowing an attacker to redirect execution flow or inject malicious code into the kernel space. The flaw particularly affects systems running Linux kernel versions prior to 5.0, where the mwifiex driver did not implement proper bounds checking for wireless frame processing. The vulnerability demonstrates the classic pattern of insufficient validation of user-supplied data, which is a fundamental principle violated in many kernel-level security issues.
The operational impact of CVE-2019-3846 extends far beyond simple network disruption, as successful exploitation can result in complete system compromise. An attacker positioned within wireless range of a vulnerable system can leverage this vulnerability to escalate privileges from regular user level to root access, effectively gaining complete control over the target machine. The memory corruption can be exploited to execute arbitrary code with kernel privileges, potentially leading to persistent backdoor installation, data exfiltration, or system-wide compromise. This vulnerability affects a broad range of devices including laptops, desktops, servers, and embedded systems that utilize Marvell wireless network adapters. The attack surface is particularly large because wireless network connections are common and often occur automatically when systems detect available networks, making exploitation relatively easy for attackers with physical proximity or network access. The vulnerability can also be chained with other exploits to create more sophisticated attack vectors, as demonstrated in various real-world exploitation scenarios where attackers have used similar memory corruption vulnerabilities to establish persistent access to compromised systems. Organizations running affected kernel versions face significant risk, particularly in environments where wireless access points are not properly secured or where users connect to untrusted wireless networks.
Mitigation strategies for CVE-2019-3846 require immediate kernel updates and proper network security controls to prevent exploitation. The most effective solution involves upgrading to Linux kernel version 5.0 or later, where the mwifiex driver includes proper bounds checking and memory validation for wireless frame processing. System administrators should also implement wireless network segmentation and authentication controls to limit exposure to malicious networks, particularly in enterprise environments where wireless access points may be compromised. Network monitoring solutions should be configured to detect and alert on suspicious wireless network activity, including malformed beacon frames or association requests that could indicate exploitation attempts. Additional mitigations include disabling wireless connectivity when not actively needed, implementing proper wireless network access controls through authentication mechanisms such as WPA2-Enterprise, and regularly scanning for vulnerable systems within the network infrastructure. The vulnerability also highlights the importance of maintaining up-to-date kernel security patches, as this issue was resolved in kernel versions released after the vulnerability was discovered. Organizations should also consider implementing runtime protection mechanisms such as kernel address space layout randomization and stack canaries to make exploitation more difficult even if a system remains vulnerable. Security teams should conduct regular vulnerability assessments focusing on kernel modules and wireless network components to identify and remediate similar issues before they can be exploited by threat actors.