{"id":"CVE-2026-121941","kind":"vulnerability","aliases":["CVE-2026-121941"],"related":[],"title":"libmt32emu: oversized SysEx messages overflow heap and crash the application","description":"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.","summary":"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.","severity":"high","cvss":8.5,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["audio","libmt32emu","midi","package"],"not_affected_if":["version-2.8.4-or-later"],"how_to_check":"- Check the installed libmt32emu version; the sources say versions before `2.8.4` are affected.\n- 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.","status":"open","published_at":"2026-11-04T13:17:28+00:00","first_seen_at":"2026-11-04T13:27:03+00:00","triaged_at":"2026-11-04T13:27:56+00:00","updated_at":"2026-11-04T13:27:56+00:00","category":"package","confidence":0.6,"triage":{"at":"2026-11-04T13:27:56Z","model":"claude-haiku-5-5","output":{"fix":"- libmt32emu: upgrade to `2.8.4` or later.","reach":"unknown","title":"libmt32emu: oversized SysEx messages overflow heap and crash the application","impact":"medium","summary":"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.","audience":"developers","category":"package","nicknames":[],"who_cares":["libmt32emu","midi","audio"],"confidence":0.6,"fix_status":"available","needs_auth":"no","worst_case":"application crashes after heap memory corruption from oversized SysEx","analyst_note":"Confirm whether the heap corruption allows more than a crash; check the linked patch and VulnCheck advisory for the exact impact and reach.","how_to_check":"- Check the installed libmt32emu version; the sources say versions before `2.8.4` are affected.\n- Find where the library is linked into your applications (for example by searching for `mt32emu_parse_stream` calls).","plain_action":"","needs_analyst":true,"not_affected_if":["version-2.8.4-or-later"],"who_is_affected":"Applications that embed libmt32emu and feed it MIDI data through the mt32emu_parse_stream API, whether from MIDI files, MIDI ports or sequencer clients. The sources describe a crash, not code execution; the sources do not say whether memory corruption can go further.","user_interaction":"unknown","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000698,"input_tokens":4219,"output_tokens":553,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-121941':13A,16A '-2026':12A,15A '-32':29B '2.8.4':51C '32768':81C 'alloc':41B,69C 'allow':62C 'api':90C 'applic':10A,48B,105C 'attack':63C,76C 'audio':17B 'buffer':55C 'byte':84C 'client':97C 'contain':52C 'corrupt':43B,99C 'crash':8A,46B,103C 'cve':11A,14A 'data':83C 'emul':26B 'feed':78C 'file':93C 'hardwar':31B 'heap':6A,40B,54C,68C,100C 'libmt32emu':1A,18B,21B,49C 'librari':24B 'memori':44B,101C 'messag':4A,36B,75C 'midi':19B,35B,92C 'midistreamparserimpl':59C 'mt':28B 'mt32emu':87C 'overflow':5A,56C 'overs':2A,32B,72C 'packag':20B 'pars':88C 'parsesysex':60C 'past':38B,66C 'port':94C 'roland':27B 'sequenc':96C 'stream':89C 'suppli':71C 'synthes':30B 'sysex':3A,34B,74C,82C 'untermin':33B,73C 'via':91C 'vulner':57C 'write':37B,65C","nicknames":[],"mitigations":[],"who_affected":"Applications that embed libmt32emu and feed it MIDI data through the mt32emu_parse_stream API, whether from MIDI files, MIDI ports or sequencer clients. The sources describe a crash, not code execution; the sources do not say whether memory corruption can go further.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"developers","plain_action":null,"pkeys":[],"ptokens":[],"labels":["audio","high","libmt32emu","midi","package"],"campaign_type":null,"first_public_at":"2026-11-04T13:17:28+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-121941","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-121941","severity":null,"published_at":"2026-11-04T13:17:28+00:00","modified_at":"2026-11-04T13:17:28+00:00","first_seen_at":"2026-11-04T13:27:03+00:00","fetched_at":"2026-11-04T13:27:03+00:00","note":null}],"documents":[{"id":67084,"url":"https://github.com/munt/munt/commit/1749f7fed5cdb3a9015acce076a1512b1615dc3b","title":"Patch: github.com","kind":"other","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Patch: github.com"},{"id":67085,"url":"https://www.vulncheck.com/advisories/libmt32emu-before-2.8.4-heap-buffer-overflow-via-midistreamparserimpl-parsesysex","title":"Third-party advisory: www.vulncheck.com","kind":"advisory","source":"nvd","publisher":"research","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":"Third-party advisory: www.vulncheck.com"}],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}