# CVE-2025-68617: fluidsynth: FluidSynth is a software synthesizer based on the SoundFont 2 specifications

CVE-2025-68617 is fixed in fluidsynth on 1 platform by DEBIAN-CVE-2025-68617 (version 2.5.2+dfsg-1), released December 23, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2025-68617
- Priority: High
- CVSS: 7.0 (high)
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Dec 23, 2025

## Description

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From versions 2.5.0 to before 2.5.2, a race condition during unloading of a DLS file can trigger a heap-based use-after-free. A concurrently running thread may be pending to unload a DLS file, leading to use of freed memory, if the synthesizer is being concurrently destroyed, or samples of the (unloaded) DLS file are concurrently used to synthesize audio. This issue has been patched in version 2.5.2. The problem will not occur, when explicitly unloading a DLS file (before synth destruction), provided that at the time of unloading, no samples of the respective file are used by active voices. The problem will not occur in versions of FluidSynth that have been compiled without native DLS support.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | fluidsynth Debian 14 | 2.5.2+dfsg-1 | [DEBIAN-CVE-2025-68617](https://patchblox.com/security/data/fix/linux/debian-cve-2025-68617.md) | Dec 23, 2025 |

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