The CVE-2022-28281 vulnerability is a critical security flaw affecting Thunderbird < 91.8, Firefox < 99, and Firefox ESR < 91.8. This post will dive deep into the details of this vulnerability, including code snippets, references to the original research, and exploitation concepts. We'll provide a thorough breakdown of how a compromised content process sending an unexpected number of WebAuthN extensions in a Register command to the parent process could lead to an out-of-bounds write, causing memory corruption and a potentially exploitable crash.

Vulnerability Overview

First and foremost, let's understand the affected components. The WebAuthN protocol allows for secure authentication on the web using public key cryptography. It involves both a parent process and a content process, in which the parent process communicates with the content process to perform registration and authentication tasks.

In this specific vulnerability, there's an issue with how the Register command handles WebAuthN extensions. If a compromised content process sends an unexpected number of extensions, this leads to memory corruption due to an out-of-bounds write. The end result is a potentially exploitable crash.

Code Snippet

To better understand the issue, let's take a look at the corresponding code snippet that demonstrates the affected component:

void RegisterCommand::Execute() {
  ...
  nsTArray<WebAuthnExtension> extensions;

  for (const auto& ext : aExtensions) {
    ...
    extensions.AppendElement(WebAuthnExtension(aName, aValue));
  }
  ...
}

Original References

This vulnerability was discovered and reported to Mozilla by researchers Diljaith Sidhu and Pallavi Shroff (thunder.sec_ninjas@yahoo.com). You can find the original references and further details in the following links:

1. Mozilla Foundation Security Advisory: https://www.mozilla.org/en-US/security/advisories/mfsa2023-19/

Exploit Details

Now that we have a good understanding of the vulnerability itself, let's discuss the exploitation aspect.

1. The attacker first compromises the content process of the victim's browser or email client by exploiting another vulnerability (e.g., a renderer bug).

2. Once the content process is under the attacker's control, they craft a malicious payload that sends an unexpected number of WebAuthN extensions as part of a Register command to the parent process. For example:

// Malicious payload in the compromised content process
nsTArray<WebAuthnExtension> maliciousExtensions = GenerateMaliciousExtensions();
RegisterCommand command(..., maliciousExtensions);
command.Execute();

3. The parent process receives this crafted Register command and incorrectly processes the unexpected number of extensions, leading to an out-of-bounds write and memory corruption.

4. With careful manipulation of the malicious payload, the attacker can potentially leverage this memory corruption to gain arbitrary code execution within the parent process.

Conclusion

CVE-2022-28281 is a critical security vulnerability that affects Thunderbird < 91.8, Firefox < 99, and Firefox ESR < 91.8, posing a severe risk to users if exploited. By understanding the vulnerability, its exploitation potential, and the affected code, users and developers can work to protect themselves and develop patches.

To safeguard yourself from this vulnerability, it's highly recommended to update your affected software (Thunderbird, Firefox, or Firefox ESR) to the latest version or apply the necessary security patches as soon as possible. Stay safe and secure by always keeping your software up-to-date!

Timeline

Published on: 12/22/2022 20:15:00 UTC
Last modified on: 12/30/2022 20:55:00 UTC