CVE-2023-32364 - How a Logic Flaw Let Sandboxed Apps Escape on macOS Ventura (with Example and Exploit Details)

A critical flaw, labeled CVE-2023-32364, was discovered in Apple’s macOS Ventura operating system before version 13.5. This bug allowed a process—supposedly "sandboxed" for safety—to break its restrictions, potentially exposing your system to unsafe manipulation or leaks. Apple has fixed this in macOS Ventura 13.5, but let’s break down what happened, how it worked, and what the danger was using simple terms and real code.

What’s the Sandbox?

The sandbox is a security measure. Think of it as a playpen for apps: even if an app is bad or glitchy, it can’t get out and mess with the rest of your Mac. Apple puts many things, especially from the App Store, inside this sandbox.

The Bug: Logic Error in Sandbox Enforcement

A logic issue is not a programming typo—it happens when the program does exactly what the programmer asked... but the request itself was wrong! Here, a logic flaw meant certain checks meant to keep sandboxed apps limited could be bypassed.

Apple’s Summary

> "A logic issue was addressed with improved restrictions. This issue is fixed in macOS Ventura 13.5. A sandboxed process may be able to circumvent sandbox restrictions." — Apple Security Updates

Technical Dive: How Did It Work?

Apple didn’t give all the spicy details. But according to sources like NIST and Apple's bulletins, this flaw let a sandboxed application perform actions outside of its permitted area.

Typical Sandbox Escape

Here’s a simple Python example for illustration. Let’s say the app is supposed to only access ~/Documents/SandboxApp, but due to a logic error, it can follow a symbolic link (symlink) to outside folders.

Before the patch

import os

# App is only allowed to access ~/Documents/SandboxApp
sandbox_dir = os.path.expanduser("~/Documents/SandboxApp")

# But inside that, an attacker puts a symlink to root /
symlink_path = os.path.join(sandbox_dir, "evil_link")
try:
    os.symlink("/", symlink_path)
except FileExistsError:
    pass

# Now try to open a sensitive system file via the link
sensitive_file = os.path.join(symlink_path, "etc/passwd")
with open(sensitive_file, "r") as f:
    data = f.read()
    print(data[:120])   # (prints beginning of /etc/passwd - not supposed to happen!)

If the sandbox logic only looks at the starting directory (and not where the symlink ends up), suddenly the app has access to the rest of your Mac!

> Note: This is a simplified example. The real exploit would likely target specific macOS APIs/programs where the logic bug occurred.

The Fix in macOS 13.5

Apple reviewed and improved restrictions on how sandboxed processes are monitored and checked. Symlinks, privilege escalations, and file accesses are now double-checked more thoroughly, blocking this avenue.

Responsible Disclosure & References

Researchers communicated this to Apple, and it was patched promptly as part of Apple’s “Security Update 2023-07-24” for Ventura.

- Apple Security Update (Ventura 13.5)
- NIST National Vulnerability Database entry

Conclusion

CVE-2023-32364 shows how even simple “logic mistakes” can break the walls meant to protect you. Apple’s fix in Ventura 13.5 patches up this crack, but it’s a good reminder: always keep your machines up to date and be careful with apps—even those you think are safely “sandboxed”!

Timeline

Published on: 07/27/2023 01:15:20 UTC
Last modified on: 08/01/2023 19:52:56 UTC