CVE-2023-44428

What it actually does

Heap-based buffer overflow during CAP file parsing due to missing length validation on user-supplied data before copying into a heap buffer, allowing arbitrary code execution in the context of the MuseScore process.

Why it matters to the business

Successful exploitation can lead to unauthorized code execution on user workstations running the affected music notation software, enabling potential data theft, persistence, or lateral movement; the issue has been public for over two years with low but slowly rising exploit probability.

How an attack unfolds

An attacker crafts a malicious CAP file that triggers the buffer overflow when parsed. The file is delivered to the victim (via web page or attachment), who must open it; once opened, the overflow allows the attacker to execute arbitrary code without further authentication.

How to fix it

Upgrade MuseScore to the latest patched release that resolves the CAP parsing flaw; block or sandbox untrusted CAP files until updates are applied.

How to confirm the fix worked

Confirm the installed MuseScore version is newer than the vulnerable build; test parsing of known-good and known-bad CAP samples in a controlled environment and review vendor release notes for the fix.

Typical attack path

1. Create malformed CAP file exploiting insufficient length checks
2. Host or send the file to the target user
3. Victim opens the file in MuseScore (user interaction required)
4. Overflow occurs during parsing and attacker-controlled code executes

How to detect it

Review endpoint logs and process creation events around MuseScore for unexpected child processes, crashes, or abnormal memory activity immediately after CAP file access; correlate with file-open telemetry from email clients or browsers.

What your security team should do

• Prioritize patching MuseScore across all endpoints
• Restrict opening of CAP files from external or untrusted sources
• Enable application allow-listing or sandboxing for music notation tools
• Update user awareness training to highlight risks of opening unknown files