Macaron Notes 5.5 contains a buffer overflow that allows an attacker to crash the application by creating notes with an excessively long string. A payload of 350,000 repeated characters pasted into a note field triggers an overflow, causing the app to terminate unexpectedly and halt normal functionality. The vulnerability results in a local denial of service, denying legitimate users access to the notebook functionality.

The vulnerable product is Macaron Notes Gear Notebook version 5.5 as distributed by macaron-notes-great-notebook. No other vendor or product versions are listed in the CNA data.

The CVSS score of 8.7 indicates high severity. No EPSS score is available, so the exploitation probability is unknown, but the lack of KEV listing suggests no widespread exploitation is documented. The attack requires the ability to create a note with arbitrary content—typically a local user or a remote user with note‑creation access, depending on the deployment type. The exploit triggers a buffer overflow that simply terminates the process, not taking system control.