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CVE-2026-61721— FluidSynth: Heap-based buffer overrun for DLS samples

Quick assessment

Affected
FluidSynth fluidsynth
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

FluidSynth 是一个基于 SoundFont 2 规范的软件合成器。在版本 2.5.0 至 2.5.6 中，原生 DLS 加载器会将由文件控制的 和 值直接赋值给样本，而未调用 或 进行验证或清理。经过精心构造的 DLS 文件可以将样本循环点设置到样本缓冲区之外，从而在音频渲染过程中触发越界读取，导致未定义行为、潜在的信息泄露以及服务拒绝（DoS）。使用 CMake 选项 设置为 OFF 编译的二进制文件不会暴露该受影响的解析器。该问题已在版本 2.5.6 中修复。

CVSS 8.0 · High
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I. Basic Information for CVE-2026-61721

Vulnerability Information
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Vulnerability Title
FluidSynth: Heap-based buffer overrun for DLS samples
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
堆缓冲区溢出
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
FluidSynth fluidsynth >= 2.5.0, < 2.5.6 -

II. Public POCs for CVE-2026-61721

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III. Intelligence Information for CVE-2026-61721

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Patches & Fixes for CVE-2026-61721 (1)

Other References for CVE-2026-61721 (2)

Same Patch Batch · FluidSynth · 2026-09-18 · 6 CVEs total

CVE-2026-58264 9.8 CRITICAL FluidSynth: Heap-based buffer overrun
CVE-2026-61714 7.8 HIGH FluidSynth: Heap Buffer Overflow in MIDI Player
CVE-2026-61723 6.8 MEDIUM FluidSynth: DLS ptbl Chunk Integer Overflow
CVE-2026-61722 6.8 MEDIUM FluidSynth: DLS Articulation Chunk Integer Overflow
CVE-2026-61720 6.2 MEDIUM FluidSynth: SF2 DMOD Chunk Unsigned Underflow

IV. Related Vulnerabilities

Same product: fluidsynth
Same vendor: FluidSynth
Same weakness: CWE-122

V. Comments for CVE-2026-61721

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