Security vulnerabilities come in all shapes and sizes, but those that let an ordinary file crash your trusted macOS application are among the scariest. CVE-2025-24139 is exactly that: a flaw addressed by Apple in macOS Ventura 13.7.3, macOS Sonoma 14.7.3, and macOS Sequoia 15.3. Let’s break down what happened, how it worked, and what you should do.

What is CVE-2025-24139?

CVE-2025-24139 is a vulnerability in Apple’s handling of certain file formats on macOS systems. When an affected version of macOS tries to parse (read and understand) a maliciously crafted file, the application parsing that file can unexpectedly quit—otherwise known as a crash.

This may sound minor, but app crashes can often be used as a stepping stone to much worse (think code execution, data loss, or even ransomware). Apple patched this issue by improving file validation and checks.

Sequoia 15.3

Full Apple advisory:
HT214075 - About the security content of macOS Sonoma 14.7.3, macOS Ventura 13.7.3, macOS Sequoia 15.3

How Did the Exploit Work?

Apple doesn’t give out all the details at once (for obvious reasons), but here’s what’s publicly available and what we can infer:

1. There’s a parser inside macOS (probably tied to Preview or Quick Look) that reads certain file types.
2. If you open a weaponized file (often sent as an email attachment, a download, or even a ZIP file previewed in Finder), the app parsing it could crash due to improper input validation.
3. The bug is in the parser code. By tricking the parser with special file data, an attacker can trigger an unexpected condition—leading to a crash.

A Simple Exploit: Proof-of-Concept

While the full details remain under wraps, we can sketch out a *typical* exploit scenario for file parser vulnerabilities. Below is an example of how attackers might create a file with invalid structure or an oversized value that confuses the parser, causing a crash.

(Note: This is a generic, educational snippet—not tied to a real macOS system file type! Do NOT use for malicious purposes.)

# Python proof-of-concept for generating a malformed file
malicious_file = "malicious.cve24139"

# Let's assume macOS expects a simple file header + data length
HEADER = b"MACVX"
# Intentionally setting a length that's way too large, or negative
LENGTH = (2**32 - 1).to_bytes(4, "big")  # xFFFFFFFF

# Junk data
PAYLOAD = b"A" * 10

with open(malicious_file, "wb") as f:
    f.write(HEADER)
    f.write(LENGTH)
    f.write(PAYLOAD)

print("Malicious file created! Try opening this with a vulnerable app.")

How does this work? If the app doesn’t properly check the value of LENGTH, it may allocate massive memory, go out of bounds, or just crash when things don’t line up.

Be Careful With Strange Files

Don’t open files from unknown sources, even if they look harmless. Attackers often hide crafted payloads in images, documents, or archives.

Official Apple Security Update:

HT214075
- Mitre CVE Record for CVE-2025-24139 (link will be updated as info is published)

Apple Security Updates Index:

Apple Security Updates

In Short

CVE-2025-24139 is a strong reminder that even something as simple as opening a file can be dangerous if your system isn’t patched. Apple’s fix—“improved checks”—means more robust file validation and fewer crashes for all of us. Update now, stay alert, and don’t let a file bring your Mac down!


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Timeline

Published on: 01/27/2025 22:15:18 UTC
Last modified on: 03/03/2025 22:45:11 UTC