CVE-2026-61720 Details
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.
A denial-of-service vulnerability has been identified in FluidSynth versions 2.5.0 through 2.5.5. The issue arises in the SF2 parser, where the DMOD modulator count is calculated based on the chunk size. The parser does not properly validate chunk sizes, allowing a crafted SF2 file with a zero-sized DMOD chunk to cause an unsigned underflow. This underflow leads to excessive memory allocation, as the parser attempts to allocate billions of SFMod structures, ultimately exhausting the process's memory and causing a crash. This vulnerability has been fixed in FluidSynth version 2.5.6.
Users are advised to update FluidSynth to version 2.5.6, which addresses this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 18, 2026CISA-ADP
Assessed Sep 21, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/FluidSynth/fluidsynth/commit/096e1ff0d09ddcac83d94923440706f76f94bc44 | [email protected] | Source CodeVendor |
| https://github.com/FluidSynth/fluidsynth/releases/tag/v2.5.6 | [email protected] | Release NotesVendor |
| https://github.com/FluidSynth/fluidsynth/security/advisories/GHSA-rmc4-c8hw-455w | [email protected] | AdvisoryRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-191 | Integer Underflow (Wrap or Wraparound) | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| FluidSynth | >= 2.5.0, <= 2.5.5 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 21, 2026 | CVE Modified | CISA-ADP |
| Sep 18, 2026 | New CVE Received | [email protected] |