Horner Automation’s Cscape is an automation software suite commonly used for programming and configuring controllers in industrial environments. In late 2022, a significant vulnerability (CVE-2022-3377) was disclosed and assigned a CVSS score of 7.8, highlighting the risk of remote code execution via a specially crafted file.

In this article, we’ll break down what CVE-2022-3377 is, how it works, and in simple terms, show why it can be dangerous. Along the way, you’ll see sample code, links to public resources, and a straightforward explanation of the possible exploit path.

What Is CVE-2022-3377?

Short Summary: Versions 9.90 SP 6 and before of Cscape don’t properly check data from FNT font files. If you open a bad FNT file, an attacker can make Cscape read from (or maybe even write to) memory it shouldn’t, executing arbitrary code on your machine.

Affected Product:  
Horner Automation Cscape, v9.90 SP 6 and earlier

Attack Vector:  
User opens a malicious .fnt file, either attached to an email, planted in a project, or downloaded by mistake.

Reported By:  
CISA, with credit to Gjoko Krstic of Applied Risk

References:  
- CISA Advisory
- MITRE CVE Entry

How the Vulnerability Works

Software like Cscape expects font files (FNT) to follow certain rules and structure. If a file does not, robust software stops loading it or throws an error. Cscape, however, did not double-check data before using it—leading to *uninitialized pointer access.*

Uninitialized Pointer? In Plain Terms...

Think of a pointer as a label on a box. If the label is empty (uninitialized), but you trust whatever’s inside and open the box anyway, you could spill hazardous stuff, or worse, let someone sneak in their own box. When Cscape uses a *label* (pointer) it never checked, a hacker can create a FNT file that tricks the program into looking where it shouldn’t—outside the allowed area (out-of-bounds read). With some clever tricks, a bad actor can use this to run their own code.

Here's a simplified and generic C code example showing what might go wrong

void loadFont(char *fntPath) {
    FontStruct *f;
    FILE *fp = fopen(fntPath, "rb");
    // ... read file header, validate size (not properly!)
    fread(&f, sizeof(FontStruct), 1, fp);
    if (f->header != x1234) {
        // Should error here, but let's say it doesn't!
    }
    // Uninitialized pointer used
    drawChar(f->glyphs[]); // glyphs not safely checked
}

If the f structure is not fully initialized (or the file fakes its content), glyphs[] could point anywhere—potentially to shellcode planted in the file.

User opens FNT in Cscape: No validation = code execution path open.

3. Uninitialized pointer is accessed: Program jumps to out-of-bounds memory (often into the file itself).
4. Attacker’s code runs: This *could* open Windows calculator, add a new user, or worse—let the attacker take over the workstation.

Quick PoC (Proof-of-Concept) Example

We don’t publish real world malware, but to demonstrate, here’s a toy Python script that makes a dummy FNT file containing a recognizable pattern where an exploit might hide code:

with open("malicious.fnt", "wb") as f:
    # Fake header
    f.write(b'\x00\x00\x00\x00')  # Padding
    f.write(b'\x34\x12')          # header field (x1234)
    # Next, fill in the area where the bug reads uninitialized pointer:
    # Here, place a NOP sled and fake shellcode for illustration
    f.write(b'\x90' * 100)        # NOP sled
    f.write(b'\xcc' * 10)         # Breakpoints ("int 3") as stand-in for payload
    # Padding to needed file size
    f.write(b'\x00' * 100)
print("Malicious FNT created.")


Note: This is NOT an actual exploit, but shows how easy it is to craft a file payload.

Prerequisites:

Attacker must convince a victim to open a malicious FNT file (common via email, USB, or bad download).

Worst Case:

Full RCE (Remote Code Execution) on the workstation, possible lateral movement in industrial networks.

Update:

Upgrade Cscape to the latest version.

Sources and Further Reading

- VulDB Entry
- CISA Official Advisory (ICS)
- MITRE CVE Report

Final Thoughts

Vulnerabilities like CVE-2022-3377 are reminders that even industrial tools need careful file validation and modern security checks. Something as simple as double-checking pointers and proper memory handling can be the difference between a safe system and a tool for attackers.

If you maintain or rely on Cscape in your industrial workflow, upgrade immediately and establish regular update practices. Never trust files from unknown sources—even fonts!


*Exclusive: This guide was created to help system integrators, industrial engineers, and security specialists understand the real risks behind CVE-2022-3377, using plain language and hands-on code snippets to illustrate the danger and fix.*

Timeline

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