In 2023, security researchers discovered a serious vulnerability affecting Kofax Power PDF, a widely used PDF reader and editor. This vulnerability is identified as CVE-2023-38089, previously tracked as ZDI-CAN-20567. It allows remote attackers to execute arbitrary code on a target system, opening doors to potentially severe breaches. In this article, we'll break down how this flaw works, who is at risk, and provide real-world context in simple terms.

What Is the Vulnerability?

CVE-2023-38089 is an Out-of-Bounds Write Remote Code Execution (RCE) vulnerability. It occurs during the way Kofax Power PDF handles a specific JavaScript object — namely, the app object and its method, like clearInterval.

When a user opens a specially crafted (malicious) PDF file, or visits a malicious page, the vulnerable application can be tricked into writing data beyond the boundaries of an intended memory buffer. This kind of flaw is called an *out-of-bounds write*, which attackers can exploit to run their own code on your computer.

Technical Details (How the Exploit Works)

The specific problem lies in how the application validates inputs to the clearInterval function of its embedded JavaScript engine. If an attacker provides a maliciously crafted argument to this function, the program may overwrite adjacent memory.

Here's a simplified illustration

// Sample malicious code embedded in a PDF's JavaScript
var buffer = [];
for (var i = ; i < 100; i++) {
    buffer.push(setInterval(function(){}, 100));
}

clearInterval(1001); // index outside the allocated buffer range!

In a vulnerable Kofax Power PDF installation, the clearInterval method does not properly check if the value (1001 in this example) actually exists within the buffer array. This can cause the program to write outside its allotted space in memory.

Overwriting memory means an attacker could inject their *own* instructions—leading to *remote code execution* (RCE). In worst cases, the attacker might install persistent malware, steal sensitive data, or take control of the computer.

Proof of Concept (PoC)

Researchers with Zero Day Initiative crafted a PoC exploit based on this vulnerability. Here’s a simplified example (conceptual, not weaponized):

// Embedded in PDF JavaScript section
app.clearInterval(99999999); // Clear an interval far beyond any valid ID

While simplified, this highlights the lack of bounds-checking. More sophisticated exploits would leverage this to overwrite precise memory locations with attacker-controlled data.

3. Cloud sharing: Attacker uploads a malicious PDF to a shared drive, waiting for someone to open it.

Because the vulnerability requires user action, common attack vectors focus on trickery and social engineering.

Mitigation steps

- Update Software: Ensure you run the latest version of Kofax Power PDF. The vendor patched this flaw after responsible disclosure.

Official references

- Zero Day Initiative Advisory ZDI-23-983
- NIST National Vulnerability Database CVE-2023-38089
- Kofax Security Updates Page

Final Thoughts

The CVE-2023-38089 vulnerability is a prime example of how a subtle programming mistake—in this case, missing checks in a widely used PDF application—can open the door for serious attacks. If you're a Kofax Power PDF user or administrator, updating your software is crucial to stay safe from exploits like this.

Stay safe, stay updated, and always be cautious with email attachments and downloads!

For more technical details, check the original advisory from Zero Day Initiative.

Timeline

Published on: 05/03/2024 02:15:50 UTC
Last modified on: 06/04/2024 17:28:11 UTC