CVE-2026-55105

HIGHPre-NVD 7.77.7—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (40th percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
7.7EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 7.7Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
7.7
EG Score
7.7HIGHmedium confidence
EG Risk
51
EG Risk 51/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity77% × 45%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
40th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 21, 2026

Last Modified

September 24, 2026

Advisory Details (3)

Auto-updated Sep 21, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_pr, github.
github Patch Available🟡 PoC Available

Fountain embeds allow arbitrary script execution in published notes and the note viewer · Advisory · laurent22/joplin · GitHub

https://github.com/laurent22/joplin/security/advisories/GHSA-f7q3-3grx-6wg9
github_pr

Desktop,Mobile,Server: Fix Fountain rendering issue

Fix merged in laurent22/joplin PR #15659 on 2026-06-12 — awaiting tagged release

https://github.com/laurent22/joplin/pull/15659
github_commit

commit 8e0812de9d79 (laurent22/joplin)

Fix landed in laurent22/joplin commit 8e0812de9d79 — awaiting tagged release

https://github.com/laurent22/joplin/commit/8e0812de9d79d1f0698bb76a8c5d7e991df9748d

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 14× in last 7d / 27× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-04 23:22 UTCEPSS rescore
  2. 2026-10-03 20:44 UTCEG score recompute
  3. 2026-10-03 14:26 UTCEPSS rescore
  4. 2026-10-02 18:17 UTCEG score recompute
  5. 2026-10-02 17:56 UTCEPSS rescore
  6. 2026-10-02 05:04 UTCEG score recompute
  7. 2026-10-01 19:50 UTCEPSS rescore
  8. 2026-10-01 02:41 UTCEG score recompute
  9. 2026-09-30 15:03 UTCEPSS rescore
  10. 2026-09-30 00:20 UTCEG score recompute
  11. 2026-09-29 15:22 UTCEPSS rescore
  12. 2026-09-29 09:21 UTCEG score recompute
  13. 2026-09-28 20:10 UTCEG score recompute
  14. 2026-09-28 13:51 UTCEPSS rescore
  15. 2026-09-27 17:37 UTCEG score recompute
  16. 2026-09-27 13:48 UTCEPSS rescore
  17. 2026-09-27 04:26 UTCEG score recompute
  18. 2026-09-26 15:59 UTCEPSS rescore
  19. 2026-09-26 02:02 UTCEG score recompute
  20. 2026-09-24 23:37 UTCEG score recompute
  21. 2026-09-24 22:57 UTCEG score recompute
  22. 2026-09-24 21:28 UTCEG score recompute
  23. 2026-09-24 14:04 UTCEPSS rescore
  24. 2026-09-22 23:39 UTCEG score recompute
  25. 2026-09-22 10:29 UTCEG score recompute
Show 2 more
  1. 2026-09-21 21:17 UTCEG score recompute
  2. 2026-09-21 21:16 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55105?
CVE-2026-55105 is a high vulnerability published on September 21, 2026. 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…
When was CVE-2026-55105 disclosed?
CVE-2026-55105 was first published on September 21, 2026, with the most recent update on September 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55105 actively exploited?
CVE-2026-55105 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (40th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55105?
CVE-2026-55105 has a CVSS base score of 7.7 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55105?
A fix for CVE-2026-55105 is available: update to the fixed version the vendor names in its advisory.

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