Bug 2538033 (CVE-2026-61723)

Summary: CVE-2026-61723 FluidSynth: FluidSynth: Denial of Service via crafted DLS file
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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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. The native DLS parser, when processing ptbl chunks, does not properly validate the size calculation, leading to an integer overflow. A remote attacker could craft a malicious DLS file that, when processed, causes the application to attempt to allocate an excessive amount of memory and read beyond chunk boundaries. This can result in a denial of service (DoS) due to excessive memory allocation and invalid reads.
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Description OSIDB Bzimport 2026-09-22 16:41:10 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 ptbl chunks with the unsigned expression cues * 4 + cbsize without checking whether the multiplication and addition fit in 32 bits. A crafted DLS file can supply a large cues value that wraps the expression and passes the chunk-size check, causing poolcues.resize(cues) to request approximately four gigabytes and the parser to read billions of entries beyond the chunk boundary. The excessive allocation and invalid reads can cause denial of service. Builds with enable-native-dls set to OFF are not exposed. This issue is fixed in version 2.5.6.