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Vulnerability · Published Sep 18, 2026 · Assigned by GitHub_M

CVE-2026-58264FluidSynth: Heap-based buffer overrun

Critical 9.8

In plain English

A critical-severity heap buffer overflow in fluidsynth from FluidSynth. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 48% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)0.6%top 51.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12fluidsynthno fix listedDEBIAN-CVE-2026-58264
Debian:13fluidsynth2.4.4+dfsg-1+deb13u3DEBIAN-CVE-2026-58264
Debian:14fluidsynth2.5.6+dfsg-1DEBIAN-CVE-2026-58264

Affected products (as reported)

VendorProductVersions
FluidSynth fluidsynth >= 1.1.2, < 2.5.6

Weakness: CWE-122 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References