# CVE-2026-58264: fluidsynth: FluidSynth is a software synthesizer based on the SoundFont 2 specifications

CVE-2026-58264 is fixed in 4 products on 1 platform, first by DEBIAN-CVE-2026-58264, released July 26, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-58264
- Priority: Urgent
- CVSS: 9.8 (critical)
- EPSS: 0.0059
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 18, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | fluidsynth Debian 13.5 (trixie) | 2.4.4+dfsg-1+deb13u3 | [DEBIAN-CVE-2026-58264](https://patchblox.com/security/data/fix/linux/debian-cve-2026-58264.md) | Jul 26, 2026 |
| Linux | fluidsynth Debian 14 | 2.5.6+dfsg-1 | [DEBIAN-CVE-2026-58264](https://patchblox.com/security/data/fix/linux/debian-cve-2026-58264.md) | Jul 26, 2026 |
| Linux | fluidsynth Ubuntu 18.04.6 LTS (bionic) | 1.1.9-1ubuntu0.1~esm1 | [fluidsynth 1.1.9-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-fluidsynth-1.1.9-1ubuntu0.1-esm1.md) | Oct 7, 2026 |
| Linux | fluidsynth Ubuntu 20.04 LTS (focal) | 2.1.1-2ubuntu0.1~esm1 | [fluidsynth 2.1.1-2ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-fluidsynth-2.1.1-2ubuntu0.1-esm1.md) | Oct 7, 2026 |
| Linux | fluidsynth Ubuntu 22.04.1 LTS (jammy) | 2.2.5-1ubuntu0.1~esm1 | [fluidsynth 2.2.5-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-fluidsynth-2.2.5-1ubuntu0.1-esm1.md) | Oct 7, 2026 |
| Linux | fluidsynth Ubuntu 24.04.5 LTS (noble) | 2.3.4-1ubuntu0.1~esm1 | [fluidsynth 2.3.4-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-fluidsynth-2.3.4-1ubuntu0.1-esm1.md) | Oct 7, 2026 |
| Linux | fluidsynth Ubuntu 26.04.1 LTS (resolute) | 2.4.8+dfsg-1ubuntu0.1~esm1 | [fluidsynth 2.4.8+dfsg-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-fluidsynth-2.4.8-dfsg-1ubuntu0.1-esm1.md) | Sep 18, 2026 |
| Linux | libfluidsynth1 Ubuntu 18.04.6 LTS (bionic) | 1.1.9-1ubuntu0.1~esm1 | [libfluidsynth1 1.1.9-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libfluidsynth1-1.1.9-1ubuntu0.1-esm1.md) | Oct 7, 2026 |
| Linux | libfluidsynth2 Ubuntu 20.04 LTS (focal) | 2.1.1-2ubuntu0.1~esm1 | [libfluidsynth2 2.1.1-2ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libfluidsynth2-2.1.1-2ubuntu0.1-esm1.md) | Oct 7, 2026 |
| Linux | libfluidsynth3 Ubuntu 22.04.1 LTS (jammy) | 2.2.5-1ubuntu0.1~esm1 | [libfluidsynth3 2.2.5-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libfluidsynth3-2.2.5-1ubuntu0.1-esm1.md) | Oct 7, 2026 |
| Linux | libfluidsynth3 Ubuntu 24.04.5 LTS (noble) | 2.3.4-1ubuntu0.1~esm1 | [libfluidsynth3 2.3.4-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libfluidsynth3-2.3.4-1ubuntu0.1-esm1.md) | Oct 7, 2026 |
| Linux | libfluidsynth3 Ubuntu 26.04.1 LTS (resolute) | 2.4.8+dfsg-1ubuntu0.1~esm1 | [libfluidsynth3 2.4.8+dfsg-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libfluidsynth3-2.4.8-dfsg-1ubuntu0.1-esm1.md) | Sep 18, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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