CVE-2021-21417Public exploit

Application crash via stale SoundFont zone pointer

Published Apr 29, 2021 · Updated Aug 3, 2024

Use-after-free in FluidSynth before 2.1.8 allows local users to crash applications by supplying a malformed SoundFont file. In load_pgen and load_igen, the parser removes an invalid global zone through a non-head list pointer, leaving the freed zone linked for later access. Triggering requires an application or embedded consumer to load the attacker-supplied file; the demonstrated consequence is a process crash.

CVSS severity5.5
Medium
EPSS probability0.94%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in FluidSynth before 2.1.8 allows local users to crash applications by supplying a malformed SoundFont file. In load_pgen and load_igen, the parser removes an invalid global zone through a non-head list pointer, leaving the freed zone linked for later access. Triggering requires an application or embedded consumer to load the attacker-supplied file; the demonstrated consequence is a process crash.

The record

CVE
CVE-2021-21417
Published
Apr 29, 2021
Updated
Aug 3, 2024
Vendor
FluidSynth
Product
FluidSynth
Classifications
CWE-416, T1204.002
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Apr 29, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.1.8

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

FluidSynth · FluidSynthversion=< 2.1.8

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
7.2GitHub, Inc.CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-416Use After Free
T1204.002Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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