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.
Affected products
fluidsynth: fluidsynth
References7
- github.com/FluidSynth/fluidsynth/security/advisories/GHSA-ffw2-… Vendor Advisory
- github.com/FluidSynth/fluidsynth/commit/685e54cdc44911ace317742… Patch
- github.com/FluidSynth/fluidsynth/commit/962b9946b5cb6b16f0c08b8… Patch
- github.com/FluidSynth/fluidsynth/issues/1717 ExploitIssue Tracking
- github.com/FluidSynth/fluidsynth/issues/1717 ExploitIssue Tracking
- github.com/FluidSynth/fluidsynth/issues/1728 Issue Tracking
- github.com/FluidSynth/fluidsynth/issues/1728 Issue Tracking
Metrics
- CVSS 3.1
-
7.0
HIGH
Score source: NVD
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 0% percentile: 12 · as of 11 November 2026
- CWE
- CWE-416
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