Hackers Could Take Control of Car Dashboard by Hacking Its Modem

Modern vehicles have evolved into sophisticated IoT devices, enhancing connectivity and driving experience. However, this advancement introduces significant security vulnerabilities.

A critical vulnerability has been identified in the Unisoc UIS7862A System-on-Chip, commonly used in automotive head units. This component integrates a modem for 3G, 4G, and 5G connectivity. Exploiting weaknesses in this modem allows unauthorized access, enabling attackers to compromise the vehicle's dashboard and user data.

Securelist analysts discovered a flaw in the modem's implementation of the 3G RLC protocol. The firmware's data packet fragmentation handling lacks sufficient bounds checking, permitting remote code execution on the modem processor. This vulnerability highlights the fragility of "black box" components in automotive supply chains.

Exploiting the Stack-Based Buffer Overflow

The vulnerability is rooted in a stack-based buffer overflow in the function that parses incoming Service Data Units. The protocol allows for an unlimited number of optional headers, which can exceed the stack buffer's capacity, leading to memory corruption.

An attacker can send a malformed packet with enough headers to trigger the overflow, overwriting the return address. The lack of stack canary protection facilitates this exploitation.

Researchers used Return-Oriented Programming techniques to bypass non-executable stack restrictions, redirecting execution to the AT+SPSERVICETYPE command handler, thereby enabling data transfer to RAM.

// Pseudo-representation of the vulnerable parsing logic void process_sdu_headers(packet_data *sdu) { uint16_t header_stack[0x5A]; // 0xB4 bytes buffer while (sdu->has_more_headers) { // Writes beyond buffer without checking bounds header_stack[index++] = read_next_header(); } }

By exploiting this vulnerability, attackers can execute arbitrary code, compromising the Android kernel and running unauthorized applications on the vehicle's head unit.

Based on reporting by Cyber Security News.