CVE-2025-56225
Published: 09 January 2026
Summary
CVE-2025-56225 is a high-severity NULL Pointer Dereference (CWE-476) vulnerability in Fluidsynth Fluidsynth. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 6.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2025-56225 affects FluidSynth versions 2.4.6 and earlier, where a null pointer dereference vulnerability exists in the fluid_synth_monopoly.c component. This flaw, classified under CWE-476, can be triggered by loading an invalid MIDI file, leading to a crash. The vulnerability received a CVSS v3.1 base score of 7.5, reflecting its network accessibility, low attack complexity, lack of required privileges or user interaction, unchanged scope, and high impact on availability with no effects on confidentiality or integrity.
Attackers can exploit this vulnerability remotely without authentication or user interaction by supplying a specially crafted invalid MIDI file to a vulnerable FluidSynth instance. Successful exploitation results in a denial-of-service condition due to application termination from the null pointer dereference, potentially disrupting services that rely on FluidSynth for MIDI processing.
Mitigation is available through a patch in the FluidSynth GitHub repository, specifically pull request #1607 addressing the issue reported in #1602. Security practitioners should update to a version incorporating this fix and validate MIDI inputs where possible to prevent exploitation.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-1717
Vulnerability details
fluidsynth-2.4.6 and earlier versions is vulnerable to Null pointer dereference in fluid_synth_monopoly.c, that can be triggered when loading an invalid midi file.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Null pointer dereference triggered by crafted MIDI input enables remote application DoS via direct exploitation of the vulnerable FluidSynth component.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Flaw remediation requires applying the vendor patch from FluidSynth PR #1607, directly eliminating the null pointer dereference when processing invalid MIDI files.
Information input validation ensures MIDI files are properly validated before processing, preventing malformed inputs from triggering the null pointer dereference crash.
Error handling implements null checks and graceful degradation to avoid application termination from the dereference during MIDI file loading.