CVE-2023-27909 - Out-Of-Bounds Write in Autodesk FBX SDK – What You Need to Know

The Autodesk® FBX® SDK is a popular library for handling FBX files—those 3D scenes, models, and animations you’ll find everywhere in gaming, film, AR/VR, and beyond. But a recent vulnerability, CVE-2023-27909, puts users and developers at risk, especially if you're using Autodesk FBX SDK 202 or earlier.

This long-read post breaks down what happened, how an attacker could exploit it, includes easy-to-read code samples, and links to trusted sources.

What is CVE-2023-27909?

CVE-2023-27909 identifies an Out-Of-Bounds Write vulnerability in Autodesk's FBX SDK (version 202 or older). If a hacker sends you a specially-crafted FBX file and you open it in an affected program, it could let them run code on your computer or snoop on private data.

In plain terms: untrusted 3D files could compromise your machine.

What’s an Out-Of-Bounds Write, Anyway?

This type of bug lets attackers shove more data into a program's memory than it should hold, tricking the computer into overwriting other data—sometimes even the instructions the computer is running!

Where’s the Problem in the Code?

The Autodesk FBX SDK reads and parses binary FBX files. When it reads in certain chunks, it allocates memory for file components without checking if the file data would overflow those slots.

A simplified (not actual source) code snippet demonstrating the bug looks like this

// Simplified pseudo-C++ for illustration
void ReadFBXData(File* f) {
  uint32_t count = ReadUInt32(f);
  // Let's say count comes from a file, but the file says '100'
  char* buffer = new char[count]; // allocates 100 bytes
  f->read(buffer, 200); // reads 200 bytes! Oops, 100 bytes go out of bounds
  // ... use buffer
  delete[] buffer;
}

If the f->read() call's length (200) isn't properly checked against count (100), it will write outside the allocated buffer. If a hacker crafts an FBX file that tricks the software into doing this, they can corrupt memory.

Scenario Example

1. Malicious FBX Created: Attacker builds a "booby-trapped" FBX file with internal headers lying about length and count fields.

Victim Loads File: Victim opens the file in a 3D app, game, or pipeline that uses the old SDK.

3. Out-Of-Bounds Write Triggers: The app trusts file fields, allocates too little memory, and writes past the buffer edge.
4. Arbitrary Code Execution: Memory overwritten includes function pointers, return addresses, or other vital control flow data.
5. Malware Runs (In Some Cases): The attacker’s code can get executed in the context of the user running the FBX program.

Proof-of-Concept: Exploiting the Vulnerability

Note: This is presented for educational and defensive purposes. Only test in a safe, offline environment!

A minimal sketch of a suspicious FBX chunk (not actual format) might be

# Python pseudo-code for building a suspect FBX file
with open("exploit.fbx", "wb") as f:
    f.write(b"Kaydara FBX Binary  \x00\x1A\x00")  # FBX header
    # Next, a chunk that claims to have 20,000 bytes of data, but only allocated 200
    f.write(struct.pack("<I", 9999))                # 'Count' (tricked)
    f.write(b"A" * 20000)                           # Way more 'A's than should fit

Feeding this to unpatched software could crash it or, if designed right, execute code from the attacker. *Real-world exploit would need to shape the payload to match internal memory expectations.*

What’s at Stake?

- Developers: If your program uses the affected FBX SDK, you must upgrade or apply workarounds—your software is at risk.
- Studios & End-Users: Any untrusted FBX file, including those downloaded from the internet, could be a trojan horse.
- Automated Pipelines: A poisoned FBX uploaded to a model hub could set off a chain reaction, jeopardizing IP and user data.

Has Autodesk Fixed This?

Yes! Autodesk addressed the bug in their security patch. The latest versions of the FBX SDK have proper boundary checks.

Release Advisory:  
- Autodesk Security Advisory for CVE-2023-27909
- Latest FBX SDK Download Page

Mitigation:

More Information & References

- NVD Entry for CVE-2023-27909
- Autodesk Security Advisory: CVE-2023-27909
- CISA Advisory: Exploitation of CVE-2023-27909 *(if/when listed)*

Takeaway

If you use the Autodesk FBX SDK—or software powered by it—update it now.  
This vulnerability is a clear route to code execution via a simple file open. Don’t let your 3D workflows turn into an attack vector.

For studios, asset managers, and app developers: spread the word, patch your pipelines, and check your imports.

Stay safe out there!

*This article was created for exclusive learning and awareness. Please always report bugs to vendors and use any sample code in a responsible, legal, and controlled environment.*

Timeline

Published on: 04/17/2023 21:15:00 UTC
Last modified on: 04/26/2023 23:05:00 UTC