The vulnerability is a timing side‑channel in the login endpoint of the Note Mark application. When a supplied username does not exist, the system returns immediately; when the username exists, bcrypt verification is performed, causing a measurable delay. An attacker can detect this delay and enumerate valid usernames. The primary impact is disclosure of valid account names, which can then be used in targeted credential attacks. This weakness is identified as CWE-208, a timing or side‑channel vulnerability that compromises confidentiality of user identities.

The affected product is enchant97's Note Mark. Versions 0.19.1 and older are vulnerable. The issue was fixed in version 0.19.2. No other vendors or product versions are listed.

With a CVSS score of 3.7, the vulnerability is considered low severity. The EPSS score is not available, suggesting no known public exploitation data. It is not listed in the KEV catalog. The likely attack vector is remote access to the login endpoint, where an attacker can measure response times over the network. If an attacker can reliably compare timings, they can enumerate all active usernames, facilitating credential stuffing or phishing attacks.