CVE-2026-49449

Joplin: KaTeX `trust:true` enables URL-allowlist bypass leading to NTLMv2 credential theft via UNC path on Windows

Published 21 Sep 2026 • Updated 21 Sep 2026

Severity: LOW

Description

Joplin is an open source note-taking and to-do application that organises notes and lists into notebooks. From 1.4.0 until 3.7.2, packages/renderer/MdToHtml/rules/katex.ts enables KaTeX's trust option for note content, allowing a note author to place a \href URL into rendered output without passing Joplin's normal URL allowlist. On Windows, clicking a link whose target is an attacker-controlled UNC path causes pathExists() to initiate SMB authentication and disclose the current user's NTLMv2 challenge-response without a warning. The unfiltered URL can also invoke other registered URL handlers, but the credential disclosure through KaTeX \href is the distinguishing demonstrated impact. This issue is fixed in version 3.7.2.

Affected products (1)

• laurent22 joplin

Problem types

• CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
• CWE-522: Insufficiently Protected Credentials
• CWE-829: Inclusion of Functionality from Untrusted Control Sphere

References (3)

• https://github.com/laurent22/joplin/security/advisories/GHSA-9m2r-pv96-jxr3
• https://github.com/laurent22/joplin/pull/15538
• https://github.com/laurent22/joplin/commit/b15472bc9654a72101b34b79c9436b3d450e2c10