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Vulnerability record · CVE-2026-58264 · published 18 September 2026

CVE-2026-58264: Heap-based buffer overflow vulnerability

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From 1.1.2 until 2.5.6, the FluidSynth command handler accepts a pitch_bend_range command whose channel argument is not bounds checked before the supplied value is written through the selected synth channel. An out-of-range channel can therefore cause an out-of-bounds heap write, leading to denial of service or possible code execution. The issue is remotely reachable when the TCP server is enabled through new_fluid_server() or fluidsynth -s, and it is locally reachable through malicious commands delivered to the FluidSynth shell on standard input. Applications that do not use the shell, command handler, or TCP server are not affected. This issue is fixed in version 2.5.6.

9.8 CVSS 3.1 Critical EPSS 0.80% · top 45.1% CWE-122 · Heap-based buffer overflow Deferred
9.8CVSS 3.1 base score
0.80%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
4References
24 Sep 2026Last modified by NVD

Description

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From 1.1.2 until 2.5.6, the FluidSynth command handler accepts a pitch_bend_range command whose channel argument is not bounds checked before the supplied value is written through the selected synth channel. An out-of-range channel can therefore cause an out-of-bounds heap write, leading to denial of service or possible code execution. The issue is remotely reachable when the TCP server is enabled through new_fluid_server() or fluidsynth -s, and it is locally reachable through malicious commands delivered to the FluidSynth shell on standard input. Applications that do not use the shell, command handler, or TCP server are not affected. This issue is fixed in version 2.5.6.

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

References

LinkTags
https://github.com/FluidSynth/fluidsynth/commit/762a3bd39a431cd45abf3bbcce7286c87909d087
https://github.com/FluidSynth/fluidsynth/pull/1796
https://github.com/FluidSynth/fluidsynth/releases/tag/v2.5.6
https://github.com/FluidSynth/fluidsynth/security/advisories/GHSA-mqmq-w63q-cj94

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Source: NIST National Vulnerability Database (record CVE-2026-58264), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.