Vulnerability · Published Sep 18, 2026 · Assigned by GitHub_M
CVE-2026-61720FluidSynth: SF2 DMOD Chunk Unsigned Underflow
Medium 6.2
In plain English
A medium-severity security flaw 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 0.2% (higher than 8% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:14 | fluidsynth | 2.5.6+dfsg-1 | DEBIAN-CVE-2026-61720 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| FluidSynth | fluidsynth | >= 2.5.0, < 2.5.6 |
Weakness: CWE-191 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H