# CVE-2026-61723: FluidSynth: DLS ptbl Chunk Integer Overflow

> A crafted DLS file triggers an integer overflow in FluidSynth's native parser, causing excessive memory allocation and denial of service.

- **Severity:** Medium 6.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Sep 2026
- **Updated:** 21 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-61723, GHSA-r4mc-v3p8-pv47, UBUNTU-CVE-2026-61723

## What is CVE-2026-61723?

CVE-2026-61723 is a medium-severity vulnerability in fluidsynth, published on 18 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-61723?


## How do I fix CVE-2026-61723?

Upgrade to a fixed version.

## Is CVE-2026-61723 being exploited?

There is no known exploitation of CVE-2026-61723 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-61723 and fix it if it is affected.

What it is: CVE-2026-61723 is a medium-severity vulnerability in fluidsynth, published on 18 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-61723 in the wild and no public exploit code.

Affected product: fluidsynth. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-61723/ (Markdown: https://insights.sbomify.com/CVE-2026-61723/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-61723
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-61723
- OSV: https://osv.dev/vulnerability/CVE-2026-61723

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-61723/
Summaries are generated and may contain mistakes; the official description above is the record.