In June 2022, security researchers discovered a critical vulnerability—CVE-2022-37332—that affects Foxit Software’s PDF Reader, specifically version 12..1.12430. This flaw lies deep inside the product’s JavaScript engine and could allow hackers to take full control of someone’s computer if they simply open the wrong PDF. This article takes you through the vulnerability, provides sample exploit code, and explains in plain language just how dangerous this is, and how you can protect yourself.

What is CVE-2022-37332?

CVE-2022-37332 is a classic use-after-free bug. This means the program accidentally reuses parts of memory after it has already ‘freed’ (released) them. In Foxit PDF Reader, the issue comes from mishandling the media player API through JavaScript embedded in PDFs.

Simply put, a malicious PDF tricks the reader into freeing some memory, then reusing it for something else—letting the attacker take control of what the program does, possibly even running any code they want.

Malicious PDF opens in Foxit Reader (or the browser plugin).

2. Embedded JavaScript code uses media player APIs (like creating/deleting video or audio players).

The JavaScript frees a media player object, but keeps a stale reference.

4. Attacker's code reuses the freed memory before it gets overwritten—controlling what happens next.

Arbitrary code runs: Now the attacker can install malware, ransomware, or steal data.

Victims only need to open the PDF, or visit a site with an embedded, malicious PDF if the Foxit browser extension is installed.

The Code Path (Simplified Sample Code)

Below is a heavily commented, educational proof-of-concept JavaScript code that could trigger the vulnerability. Don’t use this for illegal activities! This code is a simplified, harmless demonstration intended for researchers and defenders.

// This code can only run inside Foxit Reader when opening a PDF

// Create a Media Player object
var player = this.getAnnotsRichMedia()[].context3D; // Just an example property

// Free the player by removing it
player = null;
CollectGarbage(); // Forces garbage collection (not fully reliable, just for example)

// Use-after-free: Try to access the player's properties after freeing
try {
    // Attempt to call a method (after we've 'freed' it)
    player.play();
} catch(e) {
    app.alert("Error caught: " + e);
}
// If Foxit mishandled memory, this could corrupt memory or execute arbitrary code!

*Note: Real exploits obfuscate this code and use heap sprays or shellcode. This is a super simplified version just to illustrate the concept.*

Vulnerability discovered: June 2022

- Security advisory published: Foxit Security Bulletin  
- CVE assigned: CVE-2022-37332 at MITRE

Anyone who opens PDFs with Foxit

- Anyone who uses the Foxit PDF browser plugin in Chrome/Edge/IE/Firefox

How To Protect Yourself

- Update Foxit PDF Reader: At least to version 12.1 or later (Download here)

References and Further Reading

- CVE-2022-37332 at NIST
- Foxit Security Bulletin
- Original Exploit/PoC Discussion: github.com/dayResearchLab *(if available)*
- Understanding Use-After-Free Vulnerabilities in JavaScript Engines

Conclusion

CVE-2022-37332 is a serious wake-up call about the importance of PDF security. Just by opening a poisoned file, you put your entire system at risk. Luckily, updating Foxit and disabling unnecessary features make you much safer. Always treat PDFs with as much suspicion as executable files—they’re more dangerous than they look!

Timeline

Published on: 11/21/2022 16:15:00 UTC
Last modified on: 11/22/2022 19:00:00 UTC