CVE-2026-121941: Heap Overflow (CVSS 7.8)

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.

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CVSS v3.1 Score

7.8

HIGH

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0026

Probability of exploitation

0.18%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-122 CWE-122

References

Other References

https://github.com/munt/munt/blob/libmt32emu_2_8_3/mt32emu/src/MidiStreamParser.cpp#L223-L257 https://github.com/munt/munt/commit/1749f7fed5cdb3a9015acce076a1512b1615dc3b https://github.com/munt/munt/issues/149 https://hackmd.io/@haindpwn/munt-midistreamparser-oversized-sysex-heap-overflow https://www.vulncheck.com/advisories/libmt32emu-before-2.8.4-heap-buffer-overflow-via-midistreamparserimpl-parsesysex https://hackmd.io/@haindpwn/cve-2026-121941-munt-midistreamparser-oversized-sysex-heap-overflow

Frequently Asked Questions

What is CVE-2026-121941? +

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. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2026-121941? +

CVE-2026-121941 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0026, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-121941? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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