CVE-2026-61714

Name	CVE-2026-61714
Description	FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From 2.2.4 until 2.5.6, configuring synth.midi-channels above 16 allows the MIDI player to index _fluid_player_t::channel_isplaying outside its fixed-size heap allocation while tracking active channels. The resulting out-of-bounds reads and writes invoke undefined behavior and may compromise confidentiality, integrity, or availability. No crafted MIDI file is required because the unsafe condition is created by the channel-count configuration itself. Keeping synth.midi-channels at its default value of 16 avoids the vulnerable path. This issue is fixed in version 2.5.6.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
fluidsynth (PTS)	bookworm	2.3.1-2	vulnerable
	trixie	2.4.4+dfsg-1+deb13u3	fixed
	forky, sid	2.6.0+dfsg-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version
fluidsynth	source	bullseye	(not affected)
fluidsynth	source	trixie	2.4.4+dfsg-1+deb13u3
fluidsynth	source	(unstable)	2.5.6+dfsg-1

Notes

[bookworm] - fluidsynth <postponed> (Needs a non-default synth.midi-channels > 16; MIDI file channels are masked to 4 bits so a crafted file cannot reach it)
[bullseye] - fluidsynth <not-affected> (Vulnerable code not present)
https://github.com/FluidSynth/fluidsynth/security/advisories/GHSA-976m-35rw-h3m6
Introduced with: https://github.com/FluidSynth/fluidsynth/commit/6c593180ce05f8bbbd07217456bc4376a4ab4505 (v2.2.4)
Fixed by: https://github.com/FluidSynth/fluidsynth/commit/772702e00cc6acc7c607efb40283e2269211effc (v2.5.6)