Use After Free in Fluidsynth
CVE-2025-68617
FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From versions 2.5.0 to before 2.5.2, a race condition during unloading of a DLS file can trigger a heap-based use-after-free. A concurrently running thread may be pending to unload a DLS file, leading to use of freed memory, if the synthesizer is being concurrently destroyed, or samples of the (unloaded) DLS file are concurrently used to synthesize audio. This issue has been patched in version 2.5.2. The problem will not occur, when explicitly unloading a DLS file (before synth destruction), provided that at the time of unloading, no samples of the respective file are used by active voices. The problem will not occur in versions of FluidSynth that have been compiled without native DLS support.
Vulnerability class: Use-After-Free
EPSS: 0.002 (8.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.0 (High). Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.
Affected products
- Fluidsynth — versions >= 2.5.0, < 2.5.2
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
- security-advisories@github.com (Exploit, x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Patch, x_refsource_MISC)
Frequently asked questions
- What is CVE-2025-68617?
- CVE-2025-68617 is a high-severity vulnerability in Fluidsynth, classified under Use After Free. CVSS score: 7.0/10. Published 2025-12-23.
- How severe is CVE-2025-68617?
- High severity. CVSS v3 base score is 7.0 out of 10.