CVE-2019-6496 in Avastar
Summary
by MITRE
The ThreadX-based firmware on Marvell Avastar Wi-Fi devices allows remote attackers to execute arbitrary code or cause a denial of service (block pool overflow) via malformed Wi-Fi packets during identification of available Wi-Fi networks. Exploitation of the Wi-Fi device can lead to exploitation of the host application processor in some cases, but this depends on several factors including host OS hardening and the availability of DMA.
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Analysis
by VulDB Data Team • 07/02/2023
The vulnerability identified as CVE-2019-6496 represents a critical security flaw within the ThreadX-based firmware of Marvell Avastar Wi-Fi devices that operates at the network protocol level. This issue manifests through a block pool overflow condition that occurs when the device processes malformed Wi-Fi packets during the network identification and scanning process. The flaw exists within the firmware's memory management system where insufficient input validation allows attackers to craft specially crafted packets that trigger an overflow in the block pool data structure. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, though it specifically impacts heap memory management within the ThreadX real-time operating system implementation used by Marvell's Wi-Fi chipsets. The attack vector is entirely remote and does not require physical access to the device, making it particularly dangerous for wireless network environments where devices automatically scan and connect to available networks.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable arbitrary code execution on the affected devices. When attackers successfully exploit the block pool overflow, they can manipulate the firmware's memory allocation routines to inject and execute malicious code within the Wi-Fi chip's processor context. This capability represents a significant escalation from standard denial of service attacks as it can lead to complete compromise of the wireless device and potentially the entire network segment it connects to. The vulnerability's exploitation potential is further amplified by the fact that many IoT devices and embedded systems rely on similar Marvell Wi-Fi chipsets, creating a widespread attack surface. The attack requires only network-level access to deliver the malicious packets, making it particularly attractive to threat actors who may already have network reconnaissance capabilities.
The security implications of CVE-2019-6496 align with ATT&CK technique T1059.007 for command and scripting interpreter and T1068 for exploit for privilege escalation, as successful exploitation can lead to privilege escalation within the device's firmware environment. The vulnerability demonstrates the importance of proper memory management and input validation in embedded systems, particularly those running real-time operating systems like ThreadX. The attack scenario involves an attacker sending specially crafted 802.11 management frames that contain malformed data structures, which when processed by the vulnerable firmware trigger the block pool overflow condition. The root cause lies in the firmware's failure to properly validate packet lengths and structure before processing them, leading to memory corruption that can be leveraged for code execution. This vulnerability highlights the critical need for robust memory safety practices in embedded firmware development and the potential for remote code execution in network-connected devices. The exploitation process can be automated and does not require specialized tools beyond standard wireless packet crafting capabilities, making it accessible to a wide range of threat actors.
Mitigation strategies for CVE-2019-6496 focus on both immediate firmware updates and network-level protective measures. Device manufacturers should prioritize deploying firmware patches that implement proper input validation and memory boundary checking for Wi-Fi packet processing routines. Network administrators should consider implementing wireless network segmentation and monitoring to detect unusual scanning activity that might indicate exploitation attempts. The vulnerability's exploitation depends on several factors including host OS hardening and DMA capabilities, which means that even if the device firmware is compromised, complete system compromise may not occur if proper security controls are in place. Organizations should also implement network access controls and wireless intrusion detection systems to monitor for malicious Wi-Fi traffic patterns. The attack surface can be reduced by disabling unnecessary wireless scanning features and implementing strict access controls on wireless networks. Additionally, regular firmware update policies should be established to ensure that all devices receive security patches promptly. This vulnerability underscores the importance of embedded security practices and the need for continuous monitoring of networked devices for signs of exploitation attempts.