Bug 2538120 (CVE-2026-61722)

Summary: CVE-2026-61722 FluidSynth: FluidSynth: Denial of Service via DLS Articulation Chunk Integer Overflow
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in FluidSynth, a software synthesizer. This vulnerability, an integer overflow, exists in the native DLS (Downloadable Sounds) parser when it validates articulation chunks. A remote attacker could exploit this by providing a specially crafted DLS file, which causes the parser to miscalculate chunk sizes. This miscalculation leads to excessive processing and invalid memory reads, ultimately resulting in a Denial of Service (DoS) for the application.
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Description OSIDB Bzimport 2026-09-22 17:10:13 UTC 
FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From 2.5.0 until 2.5.6, the native DLS parser validates articulation chunks using the unsigned expression cbsize + connblocks * 12 without first ensuring that the multiplication and addition fit in 32 bits. A crafted DLS file can supply a large connblocks value that wraps the expression and bypasses the chunk-size check, after which the parser performs approximately one billion 12-byte iterations beyond the chunk boundary. The excessive processing and invalid reads can cause denial of service. Builds with the CMake option enable-native-dls set to OFF do not expose the parser. This issue is fixed in version 2.5.6.