---
id: "CVE-2026-121941"
kind: "vulnerability"
aliases: ["CVE-2026-121941"]
title: "libmt32emu: oversized SysEx messages overflow heap and crash the application"
severity: "high"
cvss: 8.5
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["audio", "libmt32emu", "midi", "package"]
not_affected_if: ["version-2.8.4-or-later"]
published_at: "2026-11-04T13:17:28+00:00"
first_seen_at: "2026-11-04T13:27:03+00:00"
updated_at: "2026-11-04T13:27:56+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121941", "first_seen_at": "2026-11-04T13:27:03+00:00"}]
---

# libmt32emu: oversized SysEx messages overflow heap and crash the application

libmt32emu is a library that emulates Roland MT-32 synthesizer hardware. Oversized unterminated SysEx MIDI messages write past a heap allocation, which corrupts memory and crashes the application.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed libmt32emu version; the sources say versions before `2.8.4` are affected.
- Find where the library is linked into your applications (for example by searching for `mt32emu_parse_stream` calls).

## Fix

- libmt32emu: upgrade to `2.8.4` or later.

## Timeline

- 2026-11-04T13:27:03+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121941

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/libmt32emu-before-2.8.4-heap-buffer-overflow-via-midistreamparserimpl-parsesysex
- [fix] Patch: github.com https://github.com/munt/munt/commit/1749f7fed5cdb3a9015acce076a1512b1615dc3b

## From the sources

libmt32emu before 2.8.4 contains a heap buffer overflow vulnerability in MidiStreamParserImpl::parseSysex that allows attackers to write past a heap allocation by supplying oversized unterminated SysEx messages. Attackers can feed more than 32768 SysEx data bytes through the mt32emu_parse_stream API via MIDI files, ports, or sequencer clients to corrupt heap memory and crash the application.

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