CVE-2026-40263 json
Note Mark: Username Enumeration via Login Endpoint Timing Side-Channel
published 2026-04-13 6 mo ago modified 2026-10-26 13 d ago also GHSA-w6m9-39cv-2fwp , GO-2026-5696 , EUVD-2026-23334
- cvss
- 3.7
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 17%
- public exploits
- 0
- none known
Summary
Note Mark is an open-source note-taking application. In versions 0.19.1 and prior, the login endpoint performs bcrypt password verification only when the supplied username exists, returning immediately for nonexistent usernames. This timing discrepancy allows unauthenticated attackers to enumerate valid usernames by measuring response times, enabling targeted credential attacks. This issue has been fixed in version 0.19.2.
Patch / fix
- go github.com/enchant97/note-mark/backend 0.19.2-0.20260411145025-cf4c6f6acf70
- govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
opensuse advisories openSUSE-SU-2026:21483-1
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- partial
- Assessed
- 6 mo ago
Exploit prediction
0.26% chance of exploitation in the next 30 days, higher than 17% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/enchant97/note-mark/security/advisories/GHSA-w6m9-39cv-2fwp referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N |
| GitHub | 3.1 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/enchant97/note-mark/backend | <0.19.2-0.20260411145025-cf4c6f6acf70 all versions |
0.19.2-0.20260411145025-cf4c6f6acf70 |
Affected products
- enchant97 note-mark
Classification
- Weakness
-
- CWE-208 Observable Timing Discrepancy
References
Sources
- CVE List CVE-2026-40263
- GitHub Advisory GHSA-w6m9-39cv-2fwp
- NVD CVE-2026-40263
- OSV GO-2026-5696
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