fluidsynth 2.5.0/2.5.1 DLS File Parser use after free

Summaryinfo

A vulnerability marked as critical has been reported in fluidsynth 2.5.0/2.5.1. This vulnerability affects unknown code of the component DLS File Parser. The manipulation leads to use after free. This vulnerability is documented as CVE-2025-68617. The attack can be initiated remotely. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in fluidsynth 2.5.0/2.5.1 and classified as critical. This issue affects an unknown code of the component DLS File Parser. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2025-68617 since 12/19/2025. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 279700 (Linux Distros Unpatched Vulnerability : CVE-2025-68617), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.5.2 eliminates this vulnerability. Applying the patch 685e54cdc44911ace31774260bd0c9ec89887491 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (279700). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Name

• fluidsynth

Version

• 2.5.0
• 2.5.1

License

• open-source

Website

• Product: https://github.com/FluidSynth/fluidsynth/

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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