Is CVE-2026-61720 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-61720 being exploited in the wild.

How severe is CVE-2026-61720?

Medium severity, with a CVSS score of 6.2, published 18 September 2026.

Is there a fix for CVE-2026-61720?

A patch was published on 2026-07-04: Fixed in version 2.5.6 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-61720 attacked?

It is attacked with local access or over the network, in a software library.

Am I affected by CVE-2026-61720?

Check whether you run FluidSynth at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-61720: FluidSynth SF2 DMOD chunk integer underflow

CVE-2026-61720 · Severity: medium · CVSS 6.2 · Published 2026-09-18

FluidSynth is a software synthesizer that processes SoundFont 2 files to generate audio. A malicious SF2 file with a zero-sized DMOD chunk causes an integer underflow that triggers billions of memory allocations, exhausting available memory and crashing the application. An attacker can exploit this by tricking a user or system into opening a crafted audio file, resulting in a denial of service.

Technologies: FluidSynth. Vendors: FluidSynth.

Quick answers

Is CVE-2026-61720 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-61720 being exploited in the wild.
How severe is CVE-2026-61720?: Medium severity, with a CVSS score of 6.2, published 18 September 2026.
Which products and versions are affected?: FluidSynth 2.5.0 to 2.5.5.
Is there a fix for CVE-2026-61720?: A patch was published on 2026-07-04: Fixed in version 2.5.6 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-61720 attacked?: It is attacked with local access or over the network, in a software library.
Am I affected by CVE-2026-61720?: Check whether you run FluidSynth at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The SF2 parser in FluidSynth 2.5.0–2.5.5 calculates the modulator count as chunk.size / SF_MOD_SIZE - 1 without validating that the chunk is at least one record in size. When chunk.size is zero, the unsigned arithmetic wraps to UINT_MAX, causing the parser to attempt massive memory allocations. The vulnerability exists in the DMOD chunk processing code and requires only network or local delivery of a crafted SF2 file; no authentication or user interaction is needed beyond opening the file.

Affected products

FluidSynth FluidSynth 2.5.0 to 2.5.5

Timeline

2026-09-18: disclosed
2026-07-04: patched: Fixed in version 2.5.6

References

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