CVE-2026-40263 enchant97 CVE debrief

Who should care

Defenders responsible for Note Mark applications, particularly those using versions 0.19.1 or prior, should assess exposure and prioritize upgrading to version 0.19.2. Defenders need to verify if their Note Mark application is vulnerable and upgrade to version 0.19.2 if necessary. This includes operators, platform administrators, vulnerability management teams, and security teams who manage or secure Note Mark deployments.

Why it matters

CVE-2026-40263 allows unauthenticated attackers to enumerate valid usernames in Note Mark versions 0.19.1 and prior, enabling targeted credential attacks. Defenders should verify application versions and upgrade to version 0.19.2 if necessary.

• Unauthenticated attackers can enumerate valid usernames, enabling targeted credential attacks.
• Defenders need to verify if their Note Mark application is vulnerable and upgrade to version 0.19.2 if necessary.
• Successful enumeration of valid usernames may lead to increased phishing or credential attacks against affected applications.

Technical summary

The login endpoint of Note Mark versions 0.19.1 and prior performs bcrypt password verification only when the supplied username exists. This allows unauthenticated attackers to enumerate valid usernames by measuring response times, enabling targeted credential attacks. The issue has been fixed in version 0.19.2. This vulnerability affects Note Mark applications, particularly those using versions 0.19.1 or prior, and defenders should assess exposure and prioritize upgrading to version 0.19.2. Successful enumeration of valid usernames may lead to increased phishing or credential attacks against affected applications.

Defensive priority

Defenders should prioritize verifying if their Note Mark application is version 0.19.1 or prior and upgrading to version 0.19.2 if necessary.

Recommended defensive actions

• Verify if the Note Mark application is version 0.19.1 or prior
• Upgrade to version 0.19.2 if necessary
• Monitor for potential targeted credential attacks
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD vulnerability detail page provide information on the vulnerability, including its description, CVSS score, and affected versions. The login endpoint of Note Mark versions 0.19.1 and prior performs bcrypt password verification only when the supplied username exists. This allows unauthenticated attackers to enumerate valid usernames by measuring response times, enabling targeted credential attacks. The issue has been fixed in version 0.19.2. Defenders should verify application versions and upgrade to version 0.19.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.