Medium 6.2Published Sep 18, 2026

CVE-2026-61720FluidSynth: SF2 DMOD Chunk Unsigned Underflow

Updated under an hour ago (2026-10-19 08:20 UTC)

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Exploited in the last 30 days

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From 2.5.0 until 2.5.6, the SF2 parser computes the DMOD modulator count as chunk.size / SF_MOD_SIZE - 1 without rejecting chunks smaller than one record. A crafted SF2 file containing a zero-sized DMOD chunk makes the unsigned subtraction wrap to UINT_MAX, and the parser then attempts billions of SFMod allocations. This exhausts process memory and causes denial of service. No workaround is available. This issue is fixed in version 2.5.6.

CVSS: 6.2 MEDIUM (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-191
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Sep 21, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

FluidSynth fluidsynth fluidsynth:fluidsynth (from the name)	from 2.5.0, < 2.5.6	CNA record

References

https://github.com/FluidSynth/fluidsynth/security/advisories/GHSA-rmc4-c8hw-455wx-refsource-confirm
https://github.com/FluidSynth/fluidsynth/commit/096e1ff0d09ddcac83d94923440706f76f94bc44x-refsource-misc
https://github.com/FluidSynth/fluidsynth/releases/tag/v2.5.6x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.