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Vulnerability record · CVE-2025-68617 · published 23 December 2025

CVE-2025-68617: Fluidsynth use after free vulnerability

FFluidsynth · Fluidsynth

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.

7.0 CVSS 3.1 High EPSS 0.21% · top 89.6% CWE-416 · Use after free
7.0CVSS 3.1 base score
0.21%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
7References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/FluidSynth/fluidsynth/commit/685e54cdc44911ace31774260bd0c9ec89887491 Patch
https://github.com/FluidSynth/fluidsynth/commit/962b9946b5cb6b16f0c08b89dd1b7016d4fce886 Patch
https://github.com/FluidSynth/fluidsynth/issues/1717 ExploitIssue Tracking
https://github.com/FluidSynth/fluidsynth/issues/1728 Issue Tracking
https://github.com/FluidSynth/fluidsynth/security/advisories/GHSA-ffw2-xvvp-39ch Vendor Advisory
https://github.com/FluidSynth/fluidsynth/issues/1717 ExploitIssue Tracking
https://github.com/FluidSynth/fluidsynth/issues/1728 Issue Tracking

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Source: NIST National Vulnerability Database (record CVE-2025-68617), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.