# CVE-2026-75904: libmodplug <= 0.8.9.1 - Out-of-Bounds Read in pat_smplooped via Crafted MIDI File

> An out-of-bounds read in libmodplug allows attackers to cause denial of service or disclose memory contents via a crafted MIDI file.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 18 Aug 2026
- **Updated:** 24 Sep 2026
- **Also known as:** AZL-96854, DEBIAN-CVE-2026-75904, ECHO-64f1-9158-8f37, GHSA-prc8-cg98-hxwc, OESA-2026-3602, OESA-2026-3603, OESA-2026-3604, OESA-2026-3605, OESA-2026-3734, UBUNTU-CVE-2026-75904

## What is CVE-2026-75904?

CVE-2026-75904 is a medium-severity memory corruption vulnerability in Konstanty Bialkowski libmodplug, published on 18 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

libmodplug through 0.8.9.1 contains an out-of-bounds read in pat_smplooped in src/load_pat.cpp. The function validates only the upper bound of its sample index against MAXSMP and then subtracts one before indexing the 191-byte static array pat_loops, so an index of zero reads pat_loops[-1], one byte before the array. The index is the smpno field of a parsed MIDI event, which is initialised to zero and only later overwritten from a program-change parameter, so an event reaching the note test before an instrument is assigned carries zero. A 32-byte MIDI file supplied to the library's public ModPlug_Load entry point drives the path through CSoundFile::Create, CSoundFile::ReadMID, and MID_ReadPatterns to the read. The byte read out of bounds determines whether a note event is treated as looping, so adjacent static storage influences playback state.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-75904?


## How do I fix CVE-2026-75904?

Upgrade to a fixed version.

## Is CVE-2026-75904 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-75904 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-75904 and fix it if it is affected.

What it is: CVE-2026-75904 is a medium-severity memory corruption vulnerability in Konstanty Bialkowski libmodplug, published on 18 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-75904 exists.

Affected product: Konstanty Bialkowski libmodplug. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-75904/ (Markdown: https://insights.sbomify.com/CVE-2026-75904/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-75904
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-75904
- OSV: https://osv.dev/vulnerability/CVE-2026-75904

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-75904/
Summaries are generated and may contain mistakes; the official description above is the record.