In early 2022, a critical vulnerability (CVE-2022-24955) was discovered in Foxit PDF Reader and Foxit PDF Editor — software used by millions around the world to view and edit PDFs. The issue? Both tools searched for certain Dynamic Link Libraries (DLLs) in an unsafe way, giving attackers a sneaky path to execute malicious code just by planting a file in the right spot.

This post breaks down what happened, how the bug could be exploited, and why path handling is so important for secure desktop apps.

What Is CVE-2022-24955?

CVE-2022-24955 is an “Uncontrolled Search Path Element” bug. In plain English: Foxit looked for DLLs in locations where an attacker could place a rogue DLL. If Foxit loaded that DLL, the attacker’s code would run—possibly leading to malware, ransomware, or data theft.

Foxit PDF Editor before version 11.2.1

Foxit’s official advisory calls out the update and credits the researcher who reported the bug.

Understanding the Vulnerability

On Windows, programs often use system-provided DLLs for specific features. Sometimes, a program will “look” for a DLL by name, without specifying an exact path. That means Windows searches for the DLL in this order:

Directories in the system PATH variable

If an attacker can *predict* the DLL Foxit is about to load – but Foxit doesn’t specify an absolute path – they could trick Foxit into loading their evil file instead of Microsoft’s DLL. This is called a *DLL hijack*.

Attacker crafts a malicious example.dll that, when loaded, starts a hidden malware process.

3. The attacker convinces the victim to open a tainted PDF from a folder where example.dll is present (for example, a ZIP archive).
4. When Foxit opens the PDF, it loads example.dll from the current directory instead of the Windows directory.

Real-World Exploit Example

Let’s look at sample C++ code for a DLL hijack that pops a basic calculator. (You’d replace the payload for a real attack.)

// malicious_example.cpp - Compile as DLL

#include <windows.h>

BOOL APIENTRY DllMain(HMODULE hModule,
                      DWORD  ul_reason_for_call,
                      LPVOID lpReserved) {
    if (ul_reason_for_call == DLL_PROCESS_ATTACH) {
        // Launch calc.exe when loaded
        WinExec("calc.exe", SW_SHOWNORMAL);
    }
    return TRUE;
}

Compile this code

cl /LD malicious_example.cpp

Then, rename the DLL (e.g., example.dll) and place it in the same directory as your target PDF.

Key Point: *A real attack would use a payload that steals data, drops ransomware, or gives the attacker control—not something as harmless as calc.exe.*

References to the Original Bug

- NVD entry for CVE-2022-24955
- Foxit Security Bulletins
- MITRE CVE Page
- DLL Hijacking 101 (External Guide)

Specifies absolute paths when loading known DLLs

- Avoids loading DLLs from unsafe directories (like the app’s working directory or current folder)

How to Protect Yourself

1. Update immediately: Always run the latest Foxit Reader / Editor (or any PDF tool).
2. Beware attachments: Never open PDFs or archives from unknown sources. An attacker may have included a malicious DLL.

Why Does This Keep Happening?

DLL hijacking isn’t new — it’s a well-known flaw in Windows software, but many programs slip up. Any time a developer forgets to lock down exactly *where* a DLL should load from, attackers have a chance.

Final Thoughts

CVE-2022-24955 is a classic example of how tiny mistakes in path handling can expose even widely-used apps. For a while, something as simple as opening a PDF could have compromised your computer—*unless* you stayed up to date.

If you use Foxit Reader or Editor, upgrade now. And if you make software for Windows, double-check your DLL loading code.

Stay safe!

*This article is exclusive original content. For further reading and updates, check out the official Foxit security bulletins and follow best practices for desktop app security.*

Timeline

Published on: 02/11/2022 02:15:00 UTC
Last modified on: 02/17/2022 03:22:00 UTC