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FluidSynth EUVDEUVD-2026-83375

| CVE-2026-61721 HIGH
Heap-based Buffer Overflow (CWE-122)
2026-09-18 GitHub_M
8.0
CVSS 3.1 · Vendor: GitHub_M
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Severity by source

Vendor (GitHub_M) PRIMARY
8.0 HIGH
AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H
vuln.today AI
6.1 MEDIUM

File must be loaded locally (AV:L) and requires a user/pipeline to open it (UI:R); OOB read yields partial memory disclosure (C:L), reliable crash (A:H), no integrity impact (I:N).

3.1 AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
4.0 AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

Attack Vector
Local
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
High

Lifecycle Timeline

4
POC Analysis Generated
Sep 18, 2026 - 23:22 vuln.today
Patch available
Sep 18, 2026 - 21:18 EUVD
Analysis Generated
Sep 18, 2026 - 20:35 vuln.today
CVE Published
Sep 18, 2026 - 20:00 cve.org
HIGH 8.0

DescriptionCVE.org

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From 2.5.0 until 2.5.6, the native DLS loader assigns file-controlled wsmp.loop_start and wsmp.loop_length values to samples without calling fluid_sample_validate() or fluid_sample_sanitize_loop(). A crafted DLS file can place sample loop points beyond the sample buffer, causing out-of-bounds reads during audio rendering, undefined behavior, possible memory disclosure, and denial of service. Builds compiled with the CMake option enable-native-dls set to OFF do not expose the affected parser. This issue is fixed in version 2.5.6.

AnalysisAI

Out-of-bounds reads in FluidSynth 2.5.0 through 2.5.5 can be triggered when the process loads and renders an attacker-controlled DLS soundfont, allowing memory disclosure and denial of service. Only builds compiled with the CMake option enable-native-dls enabled expose the vulnerable loader in src/sfloader/fluid_dls.cpp; builds with that option set to OFF are unaffected. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Requires (1) a FluidSynth build compiled with the CMake option enable-native-dls (the native DLS loader in src/sfloader/fluid_dls.cpp) - builds with enable-native-dls=OFF do not expose the parser and are not affected; (2) an affected version in the range 2.5.0 through 2.5.5; and (3) the target to load and render an attacker-controlled DLS file. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The vendor CVSS is 8.0 (High) with vector AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade to FluidSynth 2.5.6 (vendor-released patch), which sanitizes wsmp loop points via fluid_sample_sanitize_loop() and validates each sample with fluid_sample_validate() before it is retained; see advisory GHSA-59ph-rx8r-8p4j, commit 2354c2a9acdb26de7cdcd37c903ee108f46c0a7d, and release tag v2.5.6. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, inventory every deployment of FluidSynth and determine build configuration, since only builds compiled with the 'enable-native-dls' CMake option contain the vulnerable loader in src/sfloader/fluid_dls.cpp and builds with that option set to OFF are unaffected. …

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EUVD-2026-83375 vulnerability details – vuln.today

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