Integer overflow in Fluidsynth
CVE-2026-61720
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 v3 metric
CVSS v3 base score 6.2 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Fluidsynth — versions >= 2.5.0, < 2.5.6
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_CONFIRM)
Frequently asked questions
- What is CVE-2026-61720?
- CVE-2026-61720 is a medium-severity vulnerability in Fluidsynth, classified under Integer Underflow. CVSS score: 6.2/10. Published 2026-09-18.
- How severe is CVE-2026-61720?
- Medium severity. CVSS v3 base score is 6.2 out of 10.