CVE-2025-56225
📋 TL;DR
FluidSynth versions 2.4.6 and earlier contain a null pointer dereference vulnerability in fluid_synth_monopoly.c that can be triggered by loading a specially crafted invalid MIDI file. This vulnerability affects any application or system using FluidSynth for MIDI synthesis, potentially causing denial of service or application crashes. Users and systems that process untrusted MIDI files are at risk.
💻 Affected Systems
- FluidSynth
📦 What is this software?
Fluidsynth by Fluidsynth
⚠️ Risk & Real-World Impact
Worst Case
Application crash leading to denial of service, potentially disrupting audio services or causing system instability in embedded environments.
Likely Case
Application crash when processing malicious MIDI files, resulting in temporary service disruption.
If Mitigated
No impact if untrusted MIDI files are not processed or if the application has proper error handling.
🎯 Exploit Status
Exploitation requires the attacker to provide a malicious MIDI file that the vulnerable system processes. No authentication is needed if the system accepts external MIDI files.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.4.7 or later
Vendor Advisory: https://github.com/FluidSynth/fluidsynth/issues/1602
Restart Required: Yes
Instructions:
1. Update FluidSynth to version 2.4.7 or later. 2. For package managers: Use 'apt update && apt upgrade fluidsynth' on Debian/Ubuntu, 'yum update fluidsynth' on RHEL/CentOS, or equivalent for your distribution. 3. For source compilation: Download latest release from GitHub and rebuild. 4. Restart any services or applications using FluidSynth.
🔧 Temporary Workarounds
Restrict MIDI file processing
allConfigure applications to reject or sandbox processing of untrusted MIDI files.
Input validation
allImplement MIDI file validation before passing to FluidSynth.
🧯 If You Can't Patch
- Implement strict access controls to prevent untrusted MIDI files from reaching FluidSynth.
- Monitor for application crashes related to MIDI processing and implement automatic restart mechanisms.
🔍 How to Verify
Check if Vulnerable:
Check FluidSynth version with 'fluidsynth --version' or 'dpkg -l | grep fluidsynth' on Debian/Ubuntu, 'rpm -q fluidsynth' on RHEL/CentOS.Check Version:
fluidsynth --versionVerify Fix Applied:
Confirm version is 2.4.7 or later using version check commands.📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults when processing MIDI files
- Error messages mentioning fluid_synth_monopoly.c or null pointer dereference
Network Indicators:
- Unusual MIDI file uploads to web applications
- MIDI file transfers to systems running FluidSynth
SIEM Query:
source="application.log" AND ("segmentation fault" OR "null pointer" OR "fluid_synth")