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CVE-2026-40263— Note Mark: Username Enumeration via Login Endpoint Timing Side-Channel

Quick assessment

Affected
enchant97 note-mark
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Note Mark是Leo Spratt个人开发者的一个基于网络的Markdown笔记应用程序。 Note Mark 0.19.1及之前版本存在安全漏洞，该漏洞源于登录端点仅当提供的用户名存在时才执行bcrypt密码验证，可能导致未经身份验证的攻击者通过测量响应时间来枚举有效用户名。

CVSS 3.7 · Low EPSS 0.31% · P22

Possible ATT&CK Techniques 1 AI

T1589.001 · Credentials
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I. Basic Information for CVE-2026-40263

Vulnerability Information
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Vulnerability Title
Note Mark: Username Enumeration via Login Endpoint Timing Side-Channel
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过时间差异性导致的信息暴露
Source: CVE Program / CVE List V5
Vulnerability Title
Note Mark 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Note Mark是Leo Spratt个人开发者的一个基于网络的Markdown笔记应用程序。 Note Mark 0.19.1及之前版本存在安全漏洞，该漏洞源于登录端点仅当提供的用户名存在时才执行bcrypt密码验证，可能导致未经身份验证的攻击者通过测量响应时间来枚举有效用户名。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
enchant97 note-mark < 0.19.2 -

II. Public POCs for CVE-2026-40263

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III. Intelligence Information for CVE-2026-40263

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Patches & Fixes for CVE-2026-40263 (1)

Vendor Advisories for CVE-2026-40263 (1)

Same Patch Batch · enchant97 · 2026-04-16 · 3 CVEs total

CVE-2026-40262 8.7 HIGH Note Mark has Stored XSS via Unrestricted Asset Upload
CVE-2026-40265 5.9 MEDIUM Note Mark has Broken Access Control on Asset Download

IV. Related Vulnerabilities

Same product: note-mark
Same vendor: enchant97
Same weakness: CWE-208

V. Comments for CVE-2026-40263

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