CVE-2022-20729: Exploring the CLI Vulnerability in Cisco Firepower Threat Defense Software and How to Mitigate It

The recent disclosure of CVE-2022-20729 highlights a concerning vulnerability in the Command Line Interface (CLI) of Cisco Firepower Threat Defense (FTD) Software. This vulnerability, if successfully exploited, would allow an authenticated, local attacker to inject XML into the command parser, potentially resulting in unintended command execution and unexpected command output.

In this detailed breakdown, we will examine the specifics of CVE-2022-20729, including relevant code snippets, original source material, and details about how this exploit works. We will also provide suggestions on how to mitigate the vulnerability and protect your enterprise network from potential attacks. Our goal is to present this information in a simple, easy-to-understand language to ensure the broader community can appreciate and address the risks posed by this newly-identified threat.

Vulnerability Details

The CVE-2022-20729 vulnerability in Cisco's FTD Software originates from an insufficient input validation, which may allow an attacker to include crafted inputs within their command syntax. Given the impact of this vulnerability, it is crucial to understand its mechanics to safeguard your system effectively. To help in this regard, let's take a closer look at a sample code snippet that demonstrates the issue.

// Sample vulnerable code snippet
function process_cli_command(command) {
    var sanitized_command = sanitize_command_input(command);
    var xml_command_data = &lt;command_data&gt;${sanitized_command}&lt;/command_data&gt;;
    execute_command(xml_command_data);
}

function sanitize_command_input(input) {
    // Insufficient input validation
    return input.replace(/[\-_='"]/g, '');
}

In the sample code snippet above, the process_cli_command function accepts a command from a user, sanitizes it through the sanitize_command_input function, and formats it as XML data. However, the sanitize_command_input function fails to perform adequate input validation and sanitization, allowing an attacker to inject malicious XML content into the command as a payload.

Exploit Functioning

An attacker who can authenticate and access the target CLI could exploit this vulnerability by crafting a carefully constructed command that bypasses input validation. By injecting XML content into the command, the attacker could manipulate the command parser and achieve adverse outcomes, like disrupting system operations or gaining unauthorized access to sensitive information.

Here's an example of an attacker exploiting this vulnerability

// Attacker's malicious command
var crafted_command = "show && <inject_malicious_xml_here>";
process_cli_command(crafted_command);

In this example, an attacker concatenates a legitimate command ("show") with a malicious XML payload, thus subverting the insufficient input validation in place and injecting their XML content into the target system's command parser.

Impact

A successful exploit of CVE-2022-20729 could have severe ramifications for affected organizations. Attackers could cause unintended command execution, leading to the potential disruption of critical system processes and unauthorized access to sensitive data. As a result, security teams must prioritize addressing this vulnerability to protect their networks from possible attacks.

Mitigation Measures

To address CVE-2022-20729, Cisco has released patches that enhance input validation mechanisms in the affected FTD Software. Organizations using vulnerable releases of the software must install these patches as soon as possible to secure their systems. Information on obtaining these patches can be found in Cisco's official security advisory here.

Additionally, organizations should implement robust input validation, sanitation, and security controls in their CLI to minimize the risk of future exploits. Frequently reviewing and updating these security measures is essential for ensuring your enterprise network remains protected against emerging threats.

Conclusion

CVE-2022-20729 highlights a significant vulnerability in the CLI of Cisco FTD Software, emphasizing the need for continued vigilance and proactive action to secure enterprise networks. By understanding the mechanics of this exploit and implementing appropriate mitigation measures, organizations can protect themselves from potential attacks and maintain a secure, well-functioning network environment.

Timeline

Published on: 05/03/2022 04:15:00 UTC
Last modified on: 05/12/2022 18:12:00 UTC