CVE-2026-61721 — FluidSynth: Heap-based buffer overrun for DLS samples
FluidSynth is a software synthesizer based on the SoundFont 2 specifications. From 2.5.0 until 2.5.6, the native DLS loader assigns file-controlled wsmp.loop_start and wsmp.loop_length values to samples without calling fluid_sample_validate() or fluid_sample_sanitize_loop(). A crafted DLS file can place sample loop points beyond the sample buffer, causing out-of-bounds reads during audio rendering, undefined behavior, possible memory disclosure, and denial of service. Builds compiled with the CMake option enable-native-dls set to OFF do not expose the affected parser. This issue is fixed in version 2.5.6.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.2% (30-day exploitation probability)+1
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Fluidsynth Fluidsynth).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Fluidsynth | Fluidsynth | version >= 2.5.0, < 2.5.6 | Vulnerable | CVE Program (cve.org) e CISA ADP |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 8.0 | CVSS 3.1 | High | 2.5 | 5.5 | security-advisories@github.com via NIST National Vulnerability Database |
| 8.0 | CVSS 3.1 | High | — | — | GitHub_M via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H (score shown at the top: security-advisories@github.com) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · fluidsynth/fluidsynth
- SSVC assessment updated
- Record published
- CVSS changed · 8.0
- Source status changed · → Awaiting Analysis
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
3 on the record
Elsewhere on this site
Related CVEs (same products)
- Medium CVE-2026-111123 FluidSynth through 2.6.1 Out-of-Bounds Write via SoundFont Modulator Destination 9h
- Critical CVE-2026-58264 FluidSynth: Heap-based buffer overrun 27d
- High CVE-2026-61714 FluidSynth: Heap Buffer Overflow in MIDI Player 27d
- Medium CVE-2026-61720 FluidSynth: SF2 DMOD Chunk Unsigned Underflow 27d
- Medium CVE-2026-61722 FluidSynth: DLS Articulation Chunk Integer Overflow 27d
- Medium CVE-2026-61723 FluidSynth: DLS ptbl Chunk Integer Overflow 27d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No fixed version, patch or mitigation documented.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-61721 is "FluidSynth: Heap-based buffer overrun for DLS samples", rated High. It affects Fluidsynth (Fluidsynth); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.0 describes technical severity. EPSS 0.19% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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