CVE-2023-4259 - Uncovering Two Potential Buffer Overflow Vulnerabilities in Zephyr's eS-WiFi Driver

We're here to discuss a recently discovered security vulnerability, registered as CVE-2023-4259, that affects the Zephyr eS-WiFi driver. This vulnerability involves two potential buffer overflow issues within the driver source code that could lead to arbitrary code execution, denial of service, or other undesirable consequences. Before diving into the details, we would like to provide an overview of the Zephyr project and the eS-WiFi driver.

The Zephyr project (https://www.zephyrproject.org/) is a collaborative open-source project dedicated to building and maintaining a real-time operating system (RTOS) that is both secure and optimized for resource-constrained devices. The eS-WiFi driver, part of the Zephyr project, is designed to interface with Espressif's ESP8266 and ESP32 Wi-Fi modules, allowing developers to incorporate Wi-Fi functionality into their Zephyr-based applications easily.

Now, let's move on to CVE-2023-4259 and its implications on the security of devices running the Zephyr eS-Wifi driver.

Vulnerability Details

The CVE-2023-4259 vulnerability arises from the presence of two potential buffer overflow vulnerabilities in the Zephyr eS-WiFi driver source code. These buffer overflow vulnerabilities lie in the following locations of the driver source code:

eswifi_socket.c

Considering the criticality of these functions in the driver, exploitation of these vulnerabilities may lead to a compromise of the confidentiality, integrity, and availability of the affected devices.

To provide more context, let's delve deeper into the specifics of these vulnerabilities.

Vulnerability 1: eswifi_transport.c

In the eswifi_transport.c source code file, a potential buffer overflow vulnerability has been detected involving the eswifi_req_rsp() function. This function is responsible for parsing user input and subsequently executing commands that interact with the Wi-Fi module. It uses fixed-size buffers that may not adequately handle input data.

static int eswifi_req_rsp(struct eswifi_dev *eswifi, char *cmd, char *rsp)
{
	static char req[] = " \r\n";
	char lb[DT_INVENTEK_ESWIFI_BUS_UART_RX_BUF_SIZE];
	...
	copy_resp = rsp && (rsp != lb);
	if (rsp && copy_resp) {
	  	memcpy(lb, rsp, sizeof(lb));
	}
	...
}

As illustrated in the code snippet above, the memcpy() function is used to copy command responses from one buffer to another without performing proper bounds checking. An attacker can potentially exploit this vulnerability by sending a maliciously crafted input consisting of a command response exceeding the size of the target buffer, causing a buffer overflow.

Vulnerability 2: eswifi_socket.c

The second potential buffer overflow vulnerability is found in the eswifi_socket.c source code file, specifically in the eswifi_socket_recv() function. This function, which handles socket server traffic, is responsible for managing communication between the Wi-Fi module and the host microcontroller.

static ssize_t eswifi_socket_recv(struct eswifi_off_socket *socket,
			      void *buf, size_t max_len, uint32_t timeout)
{
	size_t bytes;
	...
	socket->bytes_total = socket->bytes_received;
	bytes = min(max_len, socket->bytes_received);
	memcpy(buf, socket->pkt.data, bytes);
	...
}

Once again, the memcpy() function is used without proper bounds checking, leading to a conceivable buffer overflow vulnerability. An attacker can take advantage of this vulnerability by sending a supposedly larger packet to crash the system or even execute arbitrary code that could impact the device's operation.

Mitigation and Remediation

Until a patch addressing CVE-2023-4259 is released, Zephyr eS-WiFi driver users are recommended to implement the following mitigations:

Apply proper input validation and bounds checking within the affected functions in the source code.

2. Keep an eye out for any security advisories or updates from the Zephyr project (https://www.zephyrproject.org/security-advisories/) and apply patches as soon as they become available.

In conclusion, by carefully adopting these protective measures, developers can continue to use the Zephyr eS-WiFi driver without risking the compromise of their devices. Stay vigilant and watch for any updates on CVE-2023-4259 to ensure the security of your Zephyr-based applications.

Timeline

Published on: 09/26/2023 00:15:11 UTC
Last modified on: 11/14/2023 03:15:09 UTC