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CVE-2025-68617

Use after free in fluidsynth

7.0 HighFix available

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From versions 2.5.0 to before 2.5.2, a race condition during unloading of a DLS file can trigger a heap-based use-after-free. A concurrently running thread may be pending to unload a DLS file, leading to use of freed memory, if the synthesizer is being concurrently destroyed, or samples of the (unloaded) DLS file are concurrently used to synthesize audio. This issue has been patched in version 2.5.2. The problem will not occur, when explicitly unloading a DLS file (before synth destruction), provided that at the time of unloading, no samples of the respective file are used by active voices. The problem will not occur in versions of FluidSynth that have been compiled without native DLS support.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
High
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

0.21%Up 0.2 points since Dec 24, 2025
90%50%10%1%

What each source reports

CVE List Score used 7.0

Use after free in fluidsynth

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From versions 2.5.0 to before 2.5.2, a race condition during unloading of a DLS file can trigger a heap-based use-after-free. A concurrently running thread may be pending to unload a DLS file, leading to use of freed memory, if the synthesizer is being concurrently destroyed, or samples of the (unloaded) DLS file are concurrently used to synthesize audio. This issue has been patched in version 2.5.2. The problem will not occur, when explicitly unloading a DLS file (before synth destruction), provided that at the time of unloading, no samples of the respective file are used by active voices. The problem will not occur in versions of FluidSynth that have been compiled without native DLS support.

Record
CVE-2025-68617
CVSS 3.1
7.0 HighCVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-416
Updated
2026-11-02
EUVDEUVD-2025-205027 7.0

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From versions 2.5.0 to before 2.5.2, a race condition during unloading of a DLS file can trigger a heap-based use-after-free. A concurrently running thread may be pending to unload a DLS file, leading to use of freed memory, if the synthesizer is being concurrently destroyed, or samples of the (unloaded) DLS file are concurrently used to synthesize audio. This issue has been patched in version 2.5.2. The problem will not occur, when explicitly unloading a DLS file (before synth destruction), provided that at the time of unloading, no samples of the respective file are used by active voices. The problem will not occur in versions of FluidSynth that have been compiled without native DLS support.

Record
EUVD-2025-205027
CVSS 3.1
7.0 HighCVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Updated
2026-11-02
NVD 7.0

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From versions 2.5.0 to before 2.5.2, a race condition during unloading of a DLS file can trigger a heap-based use-after-free. A concurrently running thread may be pending to unload a DLS file, leading to use of freed memory, if the synthesizer is being concurrently destroyed, or samples of the (unloaded) DLS file are concurrently used to synthesize audio. This issue has been patched in version 2.5.2. The problem will not occur, when explicitly unloading a DLS file (before synth destruction), provided that at the time of unloading, no samples of the respective file are used by active voices. The problem will not occur in versions of FluidSynth that have been compiled without native DLS support.

Record
CVE-2025-68617
CVSS 3.1
7.0 HighCVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-416
Updated
2026-11-02
OSV 7.0

Use after free in fluidsynth

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From versions 2.5.0 to before 2.5.2, a race condition during unloading of a DLS file can trigger a heap-based use-after-free. A concurrently running thread may be pending to unload a DLS file, leading to use of freed memory, if the synthesizer is being concurrently destroyed, or samples of the (unloaded) DLS file are concurrently used to synthesize audio. This issue has been patched in version 2.5.2. The problem will not occur, when explicitly unloading a DLS file (before synth destruction), provided that at the time of unloading, no samples of the respective file are used by active voices. The problem will not occur in versions of FluidSynth that have been compiled without native DLS support.

Record
CVE-2025-68617
CVSS 3.1
7.0 HighCVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-416
Updated
2026-11-02
OSVDEBIAN-CVE-2025-68617 7.0

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From versions 2.5.0 to before 2.5.2, a race condition during unloading of a DLS file can trigger a heap-based use-after-free. A concurrently running thread may be pending to unload a DLS file, leading to use of freed memory, if the synthesizer is being concurrently destroyed, or samples of the (unloaded) DLS file are concurrently used to synthesize audio. This issue has been patched in version 2.5.2. The problem will not occur, when explicitly unloading a DLS file (before synth destruction), provided that at the time of unloading, no samples of the respective file are used by active voices. The problem will not occur in versions of FluidSynth that have been compiled without native DLS support.

Record
DEBIAN-CVE-2025-68617
CVSS 3.1
7.0 HighCVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2025-68617 7.0

FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From versions 2.5.0 to before 2.5.2, a race condition during unloading of a DLS file can trigger a heap-based use-after-free. A concurrently running thread may be pending to unload a DLS file, leading to use of freed memory, if the synthesizer is being concurrently destroyed, or samples of the (unloaded) DLS file are concurrently used to synthesize audio. This issue has been patched in version 2.5.2. The problem will not occur, when explicitly unloading a DLS file (before synth destruction), provided that at the time of unloading, no samples of the respective file are used by active voices. The problem will not occur in versions of FluidSynth that have been compiled without native DLS support.

Record
UBUNTU-CVE-2025-68617
CVSS 3.1
7.0 HighCVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVopenSUSE-SU-2026:10004-1 No score

fluidsynth-2.5.2-1.1 on GA media

These are all security issues fixed in the fluidsynth-2.5.2-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:10004-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
fluidsynth
Debian:14
before 2.5.2+dfsg-1, plus listed versions
2.4.4+dfsg-12.4.6+dfsg-12.4.7+dfsg-12.4.7+dfsg-22.4.8+dfsg-12.5.0+dfsg-12.5.1+dfsg-12.5.1+dfsg-2
2.5.2+dfsg-1
fluidsynth
Ubuntu:Pro:14.04:LTS
All versions, plus listed versions
1.1.6-21.1.6-2ubuntu0.1~esm1
None known
fluidsynth
Ubuntu:Pro:16.04:LTS
All versions, plus listed versions
1.1.6-2build11.1.6-31.1.6-3ubuntu0.1~esm1
None known
fluidsynth
Ubuntu:Pro:18.04:LTS
All versions, plus listed versions
1.1.6-41.1.8-11.1.8-21.1.8-31.1.9-11.1.9-1ubuntu0.1~esm1
None known
fluidsynth
Ubuntu:Pro:20.04:LTS
All versions, plus listed versions
1.1.11-41.1.11-4ubuntu12.1.0-12.1.1-22.1.1-2ubuntu0.1~esm1
None known
fluidsynth
Ubuntu:Pro:22.04:LTS
All versions, plus listed versions
2.1.7-1.12.2.4-22.2.5-12.2.5-1ubuntu0.1~esm1
None known
fluidsynth
Ubuntu:Pro:24.04:LTS
All versions, plus listed versions
2.3.3-2.12.3.4-12.3.4-1build12.3.4-1build22.3.4-1build32.3.4-1ubuntu0.1~esm1
None known
fluidsynth
Ubuntu:25.10
All versions, plus listed versions
2.4.4+dfsg-12.4.7+dfsg-12.4.7+dfsg-2
None known
fluidsynth
Ubuntu:26.10
All versions, plus listed versions
2.4.8+dfsg-12.5.6+dfsg-12.5.7+dfsg-12.6.0+dfsg-1
None known
fluidsynth
Ubuntu:Pro:26.04:LTS
All versions, plus listed versions
2.4.7+dfsg-22.4.8+dfsg-12.4.8+dfsg-1ubuntu0.1~esm1
None known
fluidsynth
openSUSE:Tumbleweed
before 2.5.2-1.1
2.5.2-1.1

History

History
RecordedChangedSources
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-68617 is a high vulnerability (CVSS 7.0) in Fluidsynth, published December 23, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.21%, the 11th percentile. Fixed in fluidsynth 2.5.2+dfsg-1.

References

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