Joplin: Fountain embeds allow arbitrary script execution in published notes and the note viewer (CVE-2026-55105) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-55105

Joplin: Fountain embeds allow arbitrary script execution in published notes and the note viewer

Answer in brief

CVE-2026-55105 records a Unknown severity vulnerability in Joplin: Fountain embeds allow arbitrary script execution in published notes and the note viewer. The current sources do not mark it as known exploited. The current feed maps laurent22/joplin (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 21, 2026Updated Sep 21, 2026Source checked Sep 21, 2026First seen by HOL Sep 21, 2026Material review Sep 21, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps laurent22/joplin (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
laurent22/joplingeneric	< 3.6.15 \|\| >= 3.7.0, < 3.7.2	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for laurent22/joplin.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Sep 21, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 21, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 21, 2026

Sources and claim methodology

Upstream source description

Joplin is an open source note-taking and to-do application that organises notes and lists into notebooks. Prior to 3.6.15 and 3.7.2, packages/renderer/MdToHtml/rules/fountain.ts passes HTML generated by the vendored fountain.js renderer into note output without sanitizing it. A malicious Fountain code block can therefore execute script when Fountain rendering is enabled in desktop or mobile clients, or when a note is published through Joplin Server where Fountain rendering is enabled by default. The script can read content subsequently loaded in the reused note viewer or, when published notes are served from the same domain as server content, access data available to an authenticated browser in the server origin. This issue is fixed in versions 3.6.15 and 3.7.2.

Quoted source text, attributed separately from HOL analysis.