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Fencer Intel
high 7.2

CVE-2021-21417 json

Use after free in fluidsynth

published 5y ago modified 4mo ago also EUVD-2021-8704

cvss
7.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.9%
EPSS 0.9% chance of exploitation in 30 days, percentile 61%
public exploits
0
none known

Summary

fluidsynth is a software synthesizer based on the SoundFont 2 specifications. A use after free violation was discovered in fluidsynth, that can be triggered when loading an invalid SoundFont file.

Patch / fix

  • fluidsynth fluidsynth 2.1.8
  • fluidsynth Debian 14, Debian 13, Debian 12 2.1.7-1.1

debian advisories DEBIAN-CVE-2021-21417

  • fluidsynth Alpine 3.13 2.1.8-r0

alpine advisories ALPINE-CVE-2021-21417

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Is CVE-2021-21417 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-2021-21417 updated cvss 7.2

fluidsynth: A use after free via invalid SoundFont file

  • 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

Exploit prediction

0.94% chance of exploitation in the next 30 days, higher than 61% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/FluidSynth/fluidsynth/pull/810 referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/FluidSynth/fluidsynth/issues/808 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.2 CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:N/A:P

Affected products

  • FluidSynth fluidsynth

Classification

Weakness

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.