Vulnerability · Published Oct 15, 2026 · Assigned by VulnCheck

CVE-2026-111123FluidSynth through 2.6.1 Out-of-Bounds Write via SoundFont Modulator Destination

Medium 6.1

In plain English

A medium-severity out-of-bounds write in fluidsynth from FluidSynth. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 9% of all known vulnerabilities).

Severity (CVSS 3.1)6.1Medium

Exploit odds (30 days)0.2%top 90.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

FluidSynth through 2.6.1 contains an out-of-bounds write vulnerability that allows attackers to corrupt heap and stack memory by supplying unvalidated SoundFont modulator destination values. Attackers can craft an SF2 file with PMOD/IMOD destinations of 63 to 255 that, when loaded and played, write past the voice generator array and updated_gen_bit, causing memory corruption and crashes.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	fluidsynth	no fix listed	DEBIAN-CVE-2026-111123
Debian:13	fluidsynth	no fix listed	DEBIAN-CVE-2026-111123
Debian:14	fluidsynth	no fix listed	DEBIAN-CVE-2026-111123
Ubuntu:26.10	fluidsynth	no fix listed	UBUNTU-CVE-2026-111123

Affected products (as reported)

Vendor	Product	Versions
FluidSynth	fluidsynth	0 – through 2.6.1

Weakness: CWE-787 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H

References

https://hackmd.io/@haind-pwn/fluidsynth-sf2-modulator-dest-generator-oob-write technical-description
https://github.com/FluidSynth/fluidsynth/blob/71e85b2ca6bf48641ba7e2261d8f2640ae473773/src/synth/fluid_voice.c#L615-L623 technical-description
https://github.com/FluidSynth/fluidsynth/blob/71e85b2ca6bf48641ba7e2261d8f2640ae473773/src/synth/fluid_voice.c#L1184-L1229 technical-description
https://github.com/FluidSynth/fluidsynth/blob/71e85b2ca6bf48641ba7e2261d8f2640ae473773/src/sfloader/fluid_defsfont.c#L1609-L1611 technical-description
https://github.com/FluidSynth/fluidsynth product
VulnCheck Advisory: FluidSynth through 2.6.1 Out-of-Bounds Write via SoundFont Modulator Destination third-party-advisory