In early 2022, Apple patched a serious information disclosure and code execution issue lurking in how it handled STL files (that's "Standard Tessellation Language," commonly used for 3D models). This post breaks down what CVE-2022-22579 really means, offers some code insight, and shows how hackers might exploit it—all in accessible language.

What Is CVE-2022-22579?

CVE-2022-22579 refers to an information disclosure and code execution vulnerability that existed in Apple’s operating systems: iOS, iPadOS, macOS (Monterey and Big Sur), tvOS, and even some security updates for older versions like Catalina. Apple described it in their security update guide:

> "An information disclosure issue was addressed with improved state management. This issue is fixed in iOS 15.3 and iPadOS 15.3, tvOS 15.3, Security Update 2022-001 Catalina, macOS Monterey 12.2, macOS Big Sur 11.6.3. Processing a maliciously crafted STL file may lead to unexpected application termination or arbitrary code execution."

Why Is This a Big Deal?

STL files are common in the 3D printing and modeling world. You might open them on your Mac, import them into iOS apps, or preview them with Finder's Quick Look feature.

Before the patch, simply opening a malicious STL file could crash your device or—worse—let an attacker run code on your system. This is especially scary if you download random 3D models from the internet or get sent files by strangers.

A Simplified Look at the Bug

Based on info from security researchers and Apple’s own description, the issue was with state management when parsing STL files. In practical terms: the process that reads and interprets those STL files didn't always keep track of what it had done and where it was in the file correctly. Attackers could take advantage of this by crafting STL files that confuse the parser.

For example, they might insert way more triangles than expected, weird headers, or extra-long data chunks. When the Apple parser got confused, it could end up reading data it shouldn’t—or even running some of the attacker's code.

An ASCII STL file looks a bit like this

solid example
  facet normal   
    outer loop
      vertex   
      vertex 1  
      vertex  1 
    endloop
  endfacet
endsolid

A malicious file might abuse the format. Here's some pseudo-code to show how an STL parser could be tricked:

def parse_stl(file):
    for line in file:
        if line.startswith("facet normal"):
            normals.append(parse_normal(line))
        elif line.startswith("vertex"):
            vertices.append(parse_vertex(line))
        # what if there are a million vertices for a single facet?

If the parser doesn’t check for too many vertices per facet, or verifies the structure properly, adding tons of bogus vertices (or huge data fields) could cause heap overflows or other parsing errors—opening the door for exploits.

A real-world exploit takes advantage of the parser getting confused. Here’s the playbook

1. Attacker creates an overly complex or malformed STL file with crafted data, placing payload code or bogus vertex data.
2. Victim opens the file with a vulnerable Apple app—like Quick Look, iOS/iPadOS 3D viewer, or a 3rd party app using Apple’s STL routines.

Here’s some fake STL “junk” that might trigger an overflow (NOTE: harmless, for example only)

solid exploit
  facet normal   
    outer loop
      vertex   
      vertex 1 1 1
      vertex 2 2 2
      vertex 3 3 3   # extra vertex, not allowed!
      vertex 4 4 4   # keep adding, way past valid number
    endloop
  endfacet
endsolid

The attacker can pad this with thousands of lines, causing memory corruption.

Real-World Scenario

Imagine you download a 3D print of a cute figurine from a forum to preview on your Mac or iPad. If that STL file was malicious and you hadn’t updated your system past macOS 12.2 or iOS 15.3, just previewing the file could compromise your device.

Update Your Apple Devices!

Apple’s fix is already out. Make sure you have

- iOS/iPadOS 15.3 or later

Security Update 2022-001 Catalina

Be Wary of Unknown STL Files. Only open STL files from trusted sources.

References and Further Reading

- Apple Security Update Guide for CVE-2022-22579
- CVE Details – CVE-2022-22579
- NIST National Vulnerability Database entry for CVE-2022-22579
- 3D Printing STL File Format Overview)

Conclusion

The takeaway: CVE-2022-22579 is a reminder that even simple files like STL 3D models can be weaponized. Apple’s prompt update fixed this by making state management in parsers more robust. Stay updated, and always be careful with files from unfamiliar sources.

*Stay safe—and keep making awesome (and secure!) 3D creations.*

Timeline

Published on: 03/18/2022 18:15:00 UTC
Last modified on: 03/28/2022 15:44:00 UTC