{"id":"CVE-2026-61720","summary":"FluidSynth: SF2 DMOD Chunk Unsigned Underflow","details":"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.","aliases":["GHSA-rmc4-c8hw-455w"],"modified":"2026-10-22T16:31:16.100861535Z","published":"2026-09-18T20:03:43.989Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-191"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/61xxx/CVE-2026-61720.json"},"references":[{"type":"WEB","url":"https://github.com/FluidSynth/fluidsynth/releases/tag/v2.5.6"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/61xxx/CVE-2026-61720.json"},{"type":"ADVISORY","url":"https://github.com/FluidSynth/fluidsynth/security/advisories/GHSA-rmc4-c8hw-455w"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-61720"},{"type":"FIX","url":"https://github.com/FluidSynth/fluidsynth/commit/096e1ff0d09ddcac83d94923440706f76f94bc44"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/fluidsynth/fluidsynth","events":[{"introduced":"df432e151dcaf463b1ecc7e873803bfa19733fd3"},{"fixed":"e5b11058a619246cea42976dacb76ca54be3d45d"},{"fixed":"096e1ff0d09ddcac83d94923440706f76f94bc44"}],"database_specific":{"extracted_events":[{"strategy":"StringRangeExpression","range":[{"introduced":"2.5.0"},{"fixed":"2.5.6"}],"source":"AFFECTED_FIELD"},{"range":[{"fixed":"096e1ff0d09ddcac83d94923440706f76f94bc44"}],"source":"REFERENCES_COMMIT"},{"original_tag":"v2.5.6","range":[{"fixed":"e5b11058a619246cea42976dacb76ca54be3d45d"}],"source":"REFERENCES_TAG"}]}}],"versions":["v2.5.5","v2.5.4","v2.5.3","v2.5.2","v2.5.1","v2.5.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-61720.json","vanir_signatures":[{"digest":{"line_hashes":["65741976735742723877597808461499147360","158873129713208397340236107564649355567","27858880504209789441457038429492907366","242142550883552540884961556422285883183"],"threshold":0.9},"id":"CVE-2026-61720-ae4f73c0","signature_type":"Line","signature_version":"v1","source":"https://github.com/fluidsynth/fluidsynth/commit/e5b11058a619246cea42976dacb76ca54be3d45d","target":{"file":"src/sfloader/fluid_dls.cpp"},"deprecated":false},{"target":{"file":"src/sfloader/fluid_dls.cpp","function":"fluid_dls_font::fluid_dls_font"},"deprecated":false,"digest":{"length":9029,"function_hash":"109398306651516327573478367773148522902"},"id":"CVE-2026-61720-b1a5b579","signature_type":"Function","signature_version":"v1","source":"https://github.com/fluidsynth/fluidsynth/commit/e5b11058a619246cea42976dacb76ca54be3d45d"},{"signature_version":"v1","source":"https://github.com/fluidsynth/fluidsynth/commit/096e1ff0d09ddcac83d94923440706f76f94bc44","target":{"file":"src/sfloader/fluid_sffile.c"},"deprecated":false,"digest":{"line_hashes":["302164155491728493207593605520434230087","176165854215325228587004494937555612646","117424696281484135375524663821657841732","132081071433429816087314262319151239772","185937029896761501333968950966391326930","101835183487360498709834625490805493133","224343931534411895703299513558579259229","51188633703762147069205330528376058519"],"threshold":0.9},"id":"CVE-2026-61720-db9f190e","signature_type":"Line"},{"id":"CVE-2026-61720-e7b9a4d6","signature_type":"Function","signature_version":"v1","source":"https://github.com/fluidsynth/fluidsynth/commit/096e1ff0d09ddcac83d94923440706f76f94bc44","target":{"file":"src/sfloader/fluid_sffile.c","function":"process_info"},"deprecated":false,"digest":{"function_hash":"178773139024642537157931260649476069843","length":4463}}],"vanir_signatures_modified":"2026-10-22T16:31:16Z"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}