CVE-2026-75904
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
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.
References
- https://github.com/Konstanty/libmodplug
- https://github.com/Konstanty/libmodplug/blob/d1b97ed0020bc620a059d3675d1854b40bd2608d/src/load_mid.cpp#L829
- https://github.com/Konstanty/libmodplug/blob/d1b97ed0020bc620a059d3675d1854b40bd2608d/src/load_pat.cpp#L213-L217
- https://github.com/Konstanty/libmodplug/issues/103
- https://www.vulncheck.com/advisories/libmodplug-out-of-bounds-read-in-pat-smplooped-via-crafted-midi-file
- https://github.com/Konstanty/libmodplug/issues/103
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