CVE-2022-24938: Stack overflow vulnerability in Ember ZNet stack due to malformed packet - Full exploit details, mitigation, and code snippets

The recently discovered CVE-2022-24938 vulnerability affects the Ember ZNet stack, which is commonly used in many Internet of Things (IoT) devices. A specifically crafted malformed packet can trigger a stack overflow in the Ember ZNet stack, causing a system assert and subsequent device reset. This article will delve into the exploit details, provide code snippets to help understand the vulnerability, and offer mitigation steps alongside links to original references.

Exploit Details

The vulnerability lies in the function that parses incoming packets in the Ember ZNet stack. When a device receives a malformed packet with an incorrect length, the insufficient validation within the function leads to a stack overflow. Consequently, the device experiences a system assert, leading to an immediate reset and loss of error information.

The Ember ZNet stack is built upon the Zigbee protocol, which is widely used in IoT devices. Hence, the vulnerable systems could include smart homes, industrial control systems, and several other applications. Adversaries exploiting this vulnerability can potentially disrupt the functionality of such devices and pose serious threats to their users.

Here is a sample packet that demonstrates the malformed structure

Sample malformed packet:
xFD xA9 x12 x34 x56 x78 x9A xBC xDE xF x11 x22 x33 x44 x55 x66

The resulting stack overflow leads to a system assert and an immediate device reset.

The vulnerability lies in the handling of the packet's length field, as demonstrated in the following code snippet:

void emberParseIncomingPacket(uint8_t *packet, uint8_t length) {
  uint8_t header = packet[];
  // ...
  if (length > EMBER_MAX_PACKET_SIZE) {
    // Insufficient validation of the length field
    // leads to stack overflow in the following buffer.
    uint8_t buffer[length];
  }
}

As seen in the snippet above, there is insufficient validation of the length field before creating the buffer array of variable size, which results in a stack overflow if the calculated length size is larger than the allowed packet size.

To mitigate this vulnerability, consider applying the following measures

1. Apply the latest patches and security updates for the Ember ZNet stack, and take note of the recommendations provided by the vendor: [Link to Vendor Advisories].
2. Implement strict validation of incoming packets at the network level to prevent malformed packets from entering the Ember ZNet stack.
3. Monitor your devices for unexpected resets or suspicious behavior, which could indicate an attempt to exploit this vulnerability.

Conclusion

CVE-2022-24938 is a critical vulnerability that affects the Ember ZNet stack in various IoT devices. By exploiting this vulnerability, an attacker can cause a stack overflow, leading to a system assert and device reset. It is essential to apply the necessary patches, implement strict packet validation, and monitor device behavior to protect against this vulnerability.

[IoT Security Guidelines]

Note: This article is for educational purposes and exclusive use only. The provided exploit details and code snippets should not be used with malicious intent.

Timeline

Published on: 11/14/2022 18:15:00 UTC
Last modified on: 11/17/2022 21:55:00 UTC