CVE-2025-31200 is a critical memory corruption vulnerability that was recently patched by Apple. The flaw affects the core media frameworks on various Apple devices and could allow attackers to run malicious code simply by getting you to play a crafted audio file. Apple stated it had seen evidence of real-world exploitation in targeted attacks.

If you haven’t updated, do so immediately.

Links:
- iOS 18.4.1 Release Notes
- macOS Sequoia 15.4.1 Release Notes

The Memory Corruption Issue Explained

At the heart of CVE-2025-31200 is a memory safety bug—generally an out-of-bounds write or buffer overflow—which happens when the software fails to check the size or bounds of oncoming media streams. When a specially crafted media file is processed (think a “bad” audio file sent through an email, website, or messenger app), the software writes data where it shouldn’t, potentially overwriting crucial parts of memory like function pointers.

Bounds checking is a basic programming defense that makes sure you never read or write outside of the memory block you own. In this case, Apple’s media processing code wasn’t checking carefully enough.

// Simulated buggy parsing code (for demonstration):
void process_audio_stream(uint8_t* data, size_t len) {
    char buffer[256];
    // BAD: No check if len > 256
    memcpy(buffer, data, len);
    // If len > 256, buffer overflow occurs
}

The above C code illustrates a simple memory corruption scenario by copying too much untrusted data into a fixed-size buffer.

How the Exploit Works

1. Craft an Evil Media File: The attacker builds a special audio file that sneaks attacker-controlled data into memory.
2. Deliver the File: The file is sent to the target (maybe a link, attachment, or a direct message).

Trigger the Bug: Once opened, Apple’s media framework processes the file, causing an overflow.

4. Hijack Execution: Carefully chosen payloads can overwrite return addresses or function pointers in memory, redirecting the code flow to malicious shell code.
5. Remote Code Execution: The attacker potentially runs code as the logged-in user, gaining further access.

*Apple fixed this by strengthening bounds checking around audio data processing, making sure data cannot overflow.*

A Simple Proof of Concept (PoC)

While details of the real exploit are not public due to its sensitive, targeted nature, here’s a simplified demonstration:

# PoC: Generate an oversized audio chunk (not a real exploit, for research only)
with open('malicious-audio.wav', 'wb') as f:
    # Write fake .wav header (just to show the idea)
    f.write(b'RIFF')
    f.write((xFFFFFFFF).to_bytes(4, 'little')) # Huge file size field
    f.write(b'WAVEfmt ')                        # Pretend it's a valid format chunk
    f.write(b'\x00' * 1024)                     # Overflow area

If loaded into a vulnerable Apple device’s media parser, this could trigger an out-of-bounds write.

Impact: The Real-World Attack

Apple’s advisory explicitly states that they are aware of a report this vulnerability may have been exploited in an extremely sophisticated attack against specific targeted individuals on iOS.

Be wary of unsolicited media files, even from trusted sources.

- Enable automatic security updates, especially for iOS/macOS.
- If you’re a likely target (journalists, politicians), consider enabling Lockdown Mode on your Apple device.

Original References

- https://support.apple.com/en-us/HT201222 — Apple Security Releases
- CVE-2025-31200 on Apple Security Updates
- Lockdown Mode


Summary:
CVE-2025-31200 is a severe memory corruption bug in Apple’s media parser that was exploited in the wild for high-end, targeted attacks. If you haven’t updated your device, do it now.

Timeline

Published on: 04/16/2025 19:15:54 UTC
Last modified on: 04/18/2025 13:50:15 UTC