A newly discovered vulnerability, tagged as CVE-2022-40129, has been identified in the JavaScript engine of Foxit Software's PDF Reader, specifically version 12..1.12430. This use-after-free vulnerability has the potential to allow attackers to execute arbitrary code on the user's system if a malicious PDF document is opened or if the user visits a malicious website with the browser plugin extension enabled.

In this post, we will delve into the details of this vulnerability. We will provide code snippets as well as links to original references, as well as highlight the possible methods to exploit this vulnerability. Please note that this information is for educational purposes only and should not be used for any illegal activities.

Vulnerability Details

The use-after-free vulnerability is caused by a failure in the PDF Reader's JavaScript engine to correctly handle memory allocations when processing PDF documents. Specifically, the vulnerability resides in Foxit Software's PDF Reader when misusing the Optional Content Group (OCG) API, which results in memory locations being accessed after they have been freed.

As a consequence, an attacker can create a specially-crafted PDF document that triggers the reuse of previously freed memory, potentially leading to arbitrary code execution on the user's system. To exploit this vulnerability, an attacker needs to trick the user into opening the malicious PDF document.

Moreover, exploitation is also possible if a user visits a specially-crafted, malicious website while using a browser that has the Foxit PDF Reader plugin extension enabled.

Code Snippet

The following JavaScript code snippet demonstrates a possible implementation of this use-after-free vulnerability in the OCG API of Foxit PDF Reader:

// Sample JavaScript code that exploits use-after-free vulnerability in Foxit PDF Reader
var ocg = new OCG(); // Create a new Optional Content Group (OCG) object
ocg.name = "Test OCG";
ocg.state = false; // Set the OCG state to false (hidden)

// Add some content to the OCG
var pageCount = this.numPages; // Get the number of pages in the PDF document
this.addWatermarkFromText({
  cText: "Sample watermark",
  nStart: ,
  nEnd: pageCount - 1,
  nTextAlign: app.constants.align.center,
  nHorizAlign: app.constants.align.right,
  nVertAlign: app.constants.align.bottom,
  oCG: ocg // Add the watermark as content to the OCG object
});

// Trigger the use-after-free vulnerability
ocg = null; // Nullify the OCG object (free the memory)
app.setTimeout(function() {
  ocg.state = true; // Access the freed OCG object (use-after-free occurs)
}, 100);

Exploit

To exploit this vulnerability, an attacker can create a specially-crafted PDF document that contains the malicious JavaScript code snippet, as shown above. Then, the attacker must trick the user into opening this PDF document using Foxit PDF Reader version 12..1.12430.

Additionally, the attacker can exploit this vulnerability by creating a malicious website that loads the specially-crafted PDF document within a browser that has the Foxit PDF Reader plugin extension enabled. In this scenario, the user simply needs to visit the malicious website for the vulnerability to be exploited.

For more information about CVE-2022-40129, please refer to the following sources

- CVE-2022-40129 Details from the Common Vulnerabilities and Exposures database
- Foxit Software's Official Website
- Optional Content Group (OCG) API Documentation from Adobe (Chapter 4.10)

Conclusion

CVE-2022-40129 is a critical use-after-free vulnerability in the JavaScript engine of Foxit Software's PDF Reader version 12..1.12430. Users should avoid opening PDF documents from untrusted sources or visiting suspicious websites while using a browser with the Foxit PDF Reader plugin extension enabled. It is highly recommended to keep your software updated and apply the latest security patches provided by the vendor to protect your system from potential exploitation.

Timeline

Published on: 11/21/2022 16:15:00 UTC
Last modified on: 11/22/2022 01:07:00 UTC