Imagine cruising down the highway in your brand-new electric car when suddenly the multimedia display fills with Doom, the iconic 3D shooter game completely replacing your navigation map and vehicle controls. Shockingly, this isn’t science fiction.
Security researchers have demonstrated that this scenario is entirely possible in today’s connected vehicles, exposing a critical vulnerability in automotive head units powered by integrated cellular modems.
The proliferation of internet-connected devices extends far beyond smartphones and laptops. Modern vehicles, factories, trains, and even airplanes now rely on 3G/4G/5G connectivity through embedded modems.
Most of these modems are integrated into a System-on-Chip (SoC) architecture, containing a Communication Processor (CP) that handles network connectivity and an Application Processor (AP) running the vehicle’s operating system.
The critical problem lies in the interaction between these components at the microarchitecture level a “black box” known only to manufacturers, yet fundamental to the entire system’s security.
Researchers investigating the Unisoc UIS7862A SoC, commonly found in modern Chinese vehicle head units, discovered multiple critical vulnerabilities across the modem’s cellular protocol stack.
The most significant finding involves a stack-based buffer overflow in the 3G RLC (Radio Link Control) protocol implementation, tracked as CVE-2024-39432.
This vulnerability allows attackers to achieve remote code execution during the early stages of cellular connection, before any protective mechanisms activate.
The vulnerability exploits how the RLC protocol handles incoming Service Data Units (SDU) packets in unacknowledged mode. The protocol processes optional header fields sequentially, writing data to a 0xB4-byte stack buffer.
Since SDU packets can reach 0x5F0 bytes in size, an attacker crafting a packet with more than 90 headers can trigger a stack overflow.
Critically, this function lacks a stack canary protection, enabling attackers to overwrite return addresses and execute arbitrary code.
Modem Vulnerabilities
What makes this vulnerability particularly dangerous is that it’s the entry point for complete system compromise.
After executing code on the modem, researchers successfully performed lateral movement to the Application Processor through a hidden Direct Memory Access (DMA) device vulnerability.
This allowed them to patch the running Android kernel and execute code with the highest privileges effectively gaining complete control of the vehicle’s infotainment system.
The exploitation process involved leveraging Return Oriented Programming (ROP) techniques to manipulate Memory Protection Unit (MPU) settings, ultimately unlocking usually protected code sections for writing.
Researchers then patched the NAS (Non-Access Stratum) protocol handler, establishing persistent two-way communication with the vehicle’s system using protocol commands as a covert communication channel.
The implications extend beyond displaying Doom on dashboards. Full system compromise means attackers could manipulate vehicle controls, modify navigation data, intercept communications, and access sensitive user information.
This represents a fundamental threat to both road safety and driver privacy in an increasingly connected automotive ecosystem.
The vulnerability affects countless vehicles already on the road, particularly in markets where Chinese head units are prevalent.
Manufacturers face an urgent challenge: patching firmware across millions of deployed vehicles before attackers weaponize these techniques in real-world attacks.
Until comprehensive patches are deployed, connected vehicle owners remain vulnerable to remote hijacking through nothing more than a malicious cellular signal.
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