FluidSynth up to 2.5.5 DLS Loader fluid_sample_validate loop_start/loop_length out-of-bounds

Summaryinfo

A vulnerability identified as problematic has been detected in FluidSynth up to 2.5.5. This impacts the function fluid_sample_validate of the component DLS Loader. The manipulation of the argument loop_start/loop_length leads to out-of-bounds. This vulnerability is documented as CVE-2026-61721. The attack needs to be performed locally. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in FluidSynth up to 2.5.5. This issue affects the function fluid_sample_validate of the component DLS Loader. The manipulation of the argument loop_start/loop_length with an unknown input leads to a out-of-bounds vulnerability. Using CWE to declare the problem leads to CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From 2.5.0 until 2.5.6, the native DLS loader assigns file-controlled wsmp.loop_start and wsmp.loop_length values to samples without calling fluid_sample_validate() or fluid_sample_sanitize_loop(). A crafted DLS file can place sample loop points beyond the sample buffer, causing out-of-bounds reads during audio rendering, undefined behavior, possible memory disclosure, and denial of service. Builds compiled with the CMake option enable-native-dls set to OFF do not expose the affected parser. This issue is fixed in version 2.5.6.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-61721 since 07/10/2026. The exploitation is known to be easy. An attack has to be approached locally. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available.

Upgrading to version 2.5.6 eliminates this vulnerability.

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Productinfo

Name

• FluidSynth

Version

• 2.5.0
• 2.5.1
• 2.5.2
• 2.5.3
• 2.5.4
• 2.5.5

Website

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

CPE 2.3info

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CPE 2.2info

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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