CVE-2022-20826 - Bypassing Secure Boot Functionality in Cisco Secure Firewalls 310 Series with ASA or FTD Software

A significant vulnerability, CVE-2022-20826, has been discovered in the secure boot process of Cisco Secure Firewalls 310 Series running Cisco Adaptive Security Appliance (ASA) Software or Cisco Firepower Threat Defense (FTD) Software, which could pose a severe security risk for users. An unauthenticated attacker with physical access to the device can exploit this vulnerability to bypass the secure boot functionality, enabling them to inject malicious code and execute persistent code at boot time, breaking the chain of trust. This post aims to provide an in-depth analysis of this vulnerability, including code snippets, links to original references, and exploit details.

Vulnerability Details

The vulnerability occurs due to a logic error in the boot process of the affected devices. The secure boot process is responsible for ensuring that the device boots up only with genuine and trusted software, maintaining the integrity and security of the system. A successful exploit of this vulnerability allows an attacker to overwrite a specific memory location during the boot process of the affected device, thereby enabling the execution of malicious code with escalated privileges.

Exploit Details

An attacker would need physical access to the device to exploit this vulnerability, limiting the attack surface. The initial stages of the attack would involve connecting to the affected device using a UART (Universal Asynchronous Receiver/Transmitter) cable, a widely used standard in serial communication.

Once connected, the attacker could manipulate the device's memory during the boot process, allowing them to inject malicious code. The injected code could persist across device reboots and run with escalated privileges, breaking the device's chain of trust and facilitating further malicious activities.

The following code snippet demonstrates the manipulation of memory during the boot process

// Sample code snippet to manipulate memory during boot process
void boot_process() {
  // ... Boot process initialization code ...
  
  // Vulnerable memory location
  int memory_location = get_vulnerable_memory_location();

  // Attacker injects malicious code to memory location
  set_memory_value(memory_location, malicious_code);

  // ... Boot process continues with injected code ...
}

Mitigation and References

Cisco Systems has released security updates addressing this vulnerability, and it is highly recommended to apply the updates as soon as possible to mitigate this risk. The updates are available on Cisco's official website and can be found in the following security advisories:

1. Cisco Adaptive Security Appliance Software: Cisco Security Advisory
2. Cisco Firepower Threat Defense Software: Cisco Security Advisory

It is also recommended to implement physical security measures to prevent unauthorized individuals from gaining access to your device. This includes securing the device within locked cabinets or using tamper-evident mechanisms to deter potential attackers.

Conclusion

CVE-2022-20826 represents a critical vulnerability in the secure boot implementation of Cisco Secure Firewalls 310 Series running Cisco ASA or FTD Software. If exploited, it allows an attacker to bypass the secure boot functionality, enabling the execution of malicious code and breaking the chain of trust. To maintain the security and integrity of your device, it is crucial to apply the security updates provided by Cisco Systems and take preventative measures to secure your device from physical attacks.

Timeline

Published on: 11/15/2022 21:15:00 UTC
Last modified on: 11/18/2022 18:16:00 UTC