Bug 2538449 (CVE-2026-61720)

Summary:	CVE-2026-61720 fluidsynth: FluidSynth: Denial of Service via crafted SoundFont 2 file
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in FluidSynth, a software synthesizer. A remote attacker could exploit an unsigned integer underflow vulnerability in the SoundFont 2 (SF2) parser by providing a specially crafted SF2 file. This file, containing a zero-sized DMOD chunk, causes the parser to attempt an excessive number of memory allocations, leading to memory exhaustion and a denial of service.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
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Description OSIDB Bzimport 2026-09-22 18:35:15 UTC

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.