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Fencer Intel
critical 9.8

CVE-2026-58264 json

FluidSynth: Heap-based buffer overrun

published 4mo ago modified last mo. also EUVD-2026-83374 , GHSA-mqmq-w63q-cj94

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository FluidSynth/fluidsynth. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 48%
public exploits
0
none known

Summary

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From 1.1.2 until 2.5.6, the FluidSynth command handler accepts a pitch_bend_range command whose channel argument is not bounds checked before the supplied value is written through the selected synth channel. An out-of-range channel can therefore cause an out-of-bounds heap write, leading to denial of service or possible code execution. The issue is remotely reachable when the TCP server is enabled through new_fluid_server() or fluidsynth -s, and it is locally reachable through malicious commands delivered to the FluidSynth shell on standard input. Applications that do not use the shell, command handler, or TCP server are not affected. This issue is fixed in version 2.5.6.

Patch / fix

  • fluidsynth fluidsynth 2.5.6
  • fluidsynth Debian 13 2.4.4+dfsg-1+deb13u3
  • fluidsynth Debian 14 2.5.6+dfsg-1

debian advisories DEBIAN-CVE-2026-58264

  • fluidsynth Ubuntu Pro 14.04 LTS 1.1.6-2ubuntu0.1~esm1
  • fluidsynth Ubuntu Pro 16.04 LTS 1.1.6-3ubuntu0.1~esm1
  • fluidsynth Ubuntu Pro 18.04 LTS 1.1.9-1ubuntu0.1~esm1
  • fluidsynth Ubuntu Pro 20.04 LTS 2.1.1-2ubuntu0.1~esm1
  • fluidsynth Ubuntu Pro 22.04 LTS 2.2.5-1ubuntu0.1~esm1
  • fluidsynth Ubuntu Pro 24.04 LTS 2.3.4-1ubuntu0.1~esm1
  • fluidsynth Ubuntu Pro 26.04 LTS 2.4.8+dfsg-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2026-58264

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • fluidsynth openSUSE Tumbleweed 2.5.6-1.1

opensuse advisories openSUSE-SU-2026:11211-1

Is CVE-2026-58264 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-58264 updated cvss 9.8

fluidsynth: FluidSynth: Heap-based buffer overrun

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
last mo.

Exploit prediction

0.59% chance of exploitation in the next 30 days, higher than 48% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • FluidSynth fluidsynth

Classification

Weakness
  • CWE-122 Heap-based Buffer Overflow

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of FluidSynth/fluidsynth published their own advisory on GitHub. Reviewed sources take precedence over it.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.