CVE-2022-22739 is a recently discovered vulnerability in three popular applications: Firefox ESR (Extended Support Release) before 91.5, Firefox before 96, and Thunderbird before 91.5. The issue occurs when malicious websites manage to deceive users into accepting the launch of a program for handling an external URL protocol. In this post, we’ll delve into the details of the vulnerability, discuss the corresponding code snippets, and provide links to original references. Finally, we'll outline the exploit details and potential mitigations against the threat.

Understanding CVE-2022-22739

The vulnerability lies in the process of handling external URL protocols by Firefox, Firefox ESR, and Thunderbird. In some instances, attackers can trick users into executing malicious files by taking advantage of the way these applications accept or approve a request to launch an external handler.

Code Snippet

The code snippet below demonstrates the interaction between the user's browser and a malicious website running on the attacker's server:

<!DOCTYPE html>
<html>
<head>
<script>
function exploit() {
    window.location.href = "customprotocol://sample-parameter/";
}
</script>
</head>
<body>
<button onclick="exploit()">Click me</button>
</body>
</html>

The snippet contains a simple HTML file with a script that executes when the user clicks on the button labeled "Click me." This script redirects the user's browser to a URL using a custom protocol, such as "customprotocol://sample-parameter/". The browser must determine how to handle this custom protocol, and it may ask the user to allow launching an external application to process the custom URL.

The primary sources for the information on CVE-2022-22739 are as follows

1. Mozilla Foundation Security Advisory 2022-05 - Details the specific issue and its impact on Firefox and Firefox ESR.
2. Mozilla Foundation Security Advisory 2022-03 - Elaborates on how the vulnerability affects Thunderbird.
3. CVE-2022-22739 - Provides a concise summary of the issue, affected products, and related references.

Exploit Details

As mentioned earlier, CVE-2022-22739 allows attackers to dupe users into running malicious applications through custom URL protocol handling. The exploit's effectiveness relies on convincing the user to approve launching the external handler. Social engineering tactics, such as luring users with enticing offers or disguising the attack as a legitimate request, can amplify an attacker's chances of success.

Mitigations

To safeguard against the CVE-2022-22739 exploit, users and administrators should take the following precautionary measures:

1. Update to the latest versions: Upgrade Firefox, Firefox ESR, and Thunderbird to their respective latest versions to mitigate the vulnerability.
   - Firefox: Download the latest version
   - Firefox ESR: Download the latest version
   - Thunderbird: Download the latest version

2. Be cautious of unknown websites and external handlers: Avoid clicking on suspicious links or buttons in unfamiliar sites. Do not authorize requests to launch external applications unless you are confident they are legitimate.

3. Strengthen security awareness: Educate yourself and your organization about the potential dangers of social engineering and how attackers may attempt to manipulate trusting users.

Conclusion

CVE-2022-22739 demonstrates that even widely-used applications like Firefox, Firefox ESR, and Thunderbird can fall prey to vulnerabilities. Staying informed, verifying sources, and applying necessary updates are critical steps toward minimizing security risks. We advise users to stay vigilant to evolving threats and prioritize the security of their systems and networks.

Timeline

Published on: 12/22/2022 20:15:00 UTC
Last modified on: 12/29/2022 15:47:00 UTC