---
title: "CVE-2026-61721: FluidSynth - Out of Bounds Read & Denial of Service"
description: "FluidSynth 2.5.0 to 2.5.6 contains an out-of-bounds read caused by improper validation of wsmp.loop_start and wsmp.loop_length in the native DLS loader, letting attackers cause memory disclosure and denial of service, exploit requires crafted DLS file."
url: https://panop.io/threat-heartbeat/CVE-2026-61721/
---

# CVE-2026-61721 FluidSynth - Out of Bounds Read & Denial of Service

FluidSynth 2.5.0 to 2.5.6 contains an out-of-bounds read caused by improper validation of wsmp.loop\_start and wsmp.loop\_length in the native DLS loader, letting attackers cause memory disclosure and denial of service, exploit requires crafted DLS file.

CVSS base score 8.0 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.19% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-61721)

## Details

Type

Out of Bounds Read

Impact

Information Disclosure, Denial Of Service

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H

Published

18 September 2026

Updated

15 October 2026

Weakness

[CWE-122](https://cwe.mitre.org/data/definitions/122.html)

## Vendor fix

Update to version 2.5.6 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-61721](https://nvd.nist.gov/vuln/detail/CVE-2026-61721)
- [https://github.com/FluidSynth/fluidsynth/commit/2354c2a9acdb26de7cdcd37c903ee108f46c0a7d](https://github.com/FluidSynth/fluidsynth/commit/2354c2a9acdb26de7cdcd37c903ee108f46c0a7d)
- [https://github.com/FluidSynth/fluidsynth/releases/tag/v2.5.6](https://github.com/FluidSynth/fluidsynth/releases/tag/v2.5.6)
- [https://github.com/FluidSynth/fluidsynth/security/advisories/GHSA-59ph-rx8r-8p4j](https://github.com/FluidSynth/fluidsynth/security/advisories/GHSA-59ph-rx8r-8p4j)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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