In this long-read post, we will be diving deep into the details of the CVE-2023-4046 vulnerability, which affects Firefox versions earlier than 116, Firefox ESR versions prior to 102.14, and Firefox ESR versions below 115.1. This particular vulnerability arises in specific circumstances when a stale value is used for a global variable in WebAssembly (WASM) Just-In-Time (JIT) analysis. This can lead to incorrect compilation and a potentially exploitable crash in the content process. Throughout this post, we will explore code snippets, refer to original sources, and outline the exploit details.

Breaking down the CVE-2023-4046 vulnerability

In certain scenarios, when WASM JIT analysis is performed, a stale value is used for a global variable, resulting in incorrect compilation. This issue stems from a coding oversight in the implementation of the JIT compiler for WASM. The primary concern here is that this could potentially lead to exploitable crashes in the content process.

To better understand the vulnerability, let's take a look at a simplified code snippet that demonstrates the issue:

function wasmFunction(globalVar) {
  // ... Some computation here

  if (condition) {
    // ... Some code that might be affected by the stale value of globalVar
  }
}

In the code snippet above, globalVar is a global variable that is being used within the wasmFunction. If the value of globalVar is stale when it is used in the if block, then the outcome of the code might be incorrect.

1. Bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=CVE-2023-4046
2. Mozilla Security Advisory: https://www.mozilla.org/en-US/security/advisories/mfsa2023-04/
3. WebAssembly: https://webassembly.org/

Exploit details

Although Mozilla, the developer of Firefox, has not released any information on specific exploits that take advantage of the CVE-2023-4046 vulnerability, its potential impact cannot be ignored. Attackers could craft a malicious website with WASM code that takes advantage of this oversight and causes incorrect compilation, ultimately leading to crashes in the content process. This crash could then potentially be exploited to execute arbitrary code, access sensitive data, or perform other malicious activities.

To mitigate this vulnerability, Mozilla has released updates fixing this bug in newer versions of Firefox and Firefox ESR. Users are strongly encouraged to update their browsers to the latest version to ensure their system is protected from this vulnerability.

In conclusion, the CVE-2023-4046 vulnerability poses a risk to users running older versions of Firefox and Firefox ESR due to the potential for incorrect compilation and content process crashes. By understanding the underlying issue and staying informed of updates, users can keep their systems protected and maintain a secure browsing experience.

Timeline

Published on: 08/01/2023 15:15:00 UTC
Last modified on: 08/09/2023 21:15:00 UTC