CVE-2025-68617
📋 TL;DR
A race condition in FluidSynth versions 2.5.0 to 2.5.1 allows heap-based use-after-free when unloading DLS files concurrently with synthesizer destruction or audio synthesis. This vulnerability could lead to crashes or arbitrary code execution. Systems using FluidSynth with native DLS support are affected.
💻 Affected Systems
- FluidSynth
📦 What is this software?
Fluidsynth by Fluidsynth
⚠️ Risk & Real-World Impact
Worst Case
Arbitrary code execution leading to full system compromise, denial of service, or data corruption.
Likely Case
Application crash or instability when unloading DLS files during concurrent operations.
If Mitigated
No impact if DLS files are explicitly unloaded before synth destruction with no active voices using samples.
🎯 Exploit Status
Exploitation requires concurrent thread operations with specific timing conditions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.5.2
Vendor Advisory: https://github.com/FluidSynth/fluidsynth/security/advisories/GHSA-ffw2-xvvp-39ch
Restart Required: Yes
Instructions:
1. Download FluidSynth 2.5.2 from official repository. 2. Compile and install following build instructions. 3. Restart any applications using FluidSynth.
🔧 Temporary Workarounds
Disable DLS support
linuxRecompile FluidSynth without native DLS support to eliminate vulnerability.
./configure --disable-dls
make
sudo make install
Avoid concurrent DLS unloading
allEnsure DLS files are explicitly unloaded before synth destruction with no active voices using samples.
🧯 If You Can't Patch
- Isolate applications using FluidSynth to minimize attack surface.
- Monitor for crashes or abnormal behavior in FluidSynth processes.
🔍 How to Verify
Check if Vulnerable:
Check FluidSynth version and DLS support: fluidsynth --version | grep -E '2\.5\.[01]'Check Version:
fluidsynth --versionVerify Fix Applied:
Confirm version is 2.5.2 or higher: fluidsynth --version | grep '2\.5\.2'📡 Detection & Monitoring
Log Indicators:
- Segmentation fault or crash logs from FluidSynth processes
- Memory access violation errors
Network Indicators:
- Not applicable - local vulnerability
SIEM Query:
Process crashes with 'fluidsynth' in command line or error messages containing 'use-after-free' or 'DLS'🔗 References
- https://github.com/FluidSynth/fluidsynth/commit/685e54cdc44911ace31774260bd0c9ec89887491
- https://github.com/FluidSynth/fluidsynth/commit/962b9946b5cb6b16f0c08b89dd1b7016d4fce886
- https://github.com/FluidSynth/fluidsynth/issues/1717
- https://github.com/FluidSynth/fluidsynth/issues/1728
- https://github.com/FluidSynth/fluidsynth/security/advisories/GHSA-ffw2-xvvp-39ch
- https://github.com/FluidSynth/fluidsynth/issues/1717
- https://github.com/FluidSynth/fluidsynth/issues/1728
