CVE-2026-100639

HIGHPre-NVD 8.88.8—
EchelonGraph scoreHIGH confidence

Score 8.8 from GitHub Security Advisory (severity: HIGH) published 2026-09-26. A secondary CVSS source baseline 8.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
8.8EG
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: 8.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

SiYuan v3.8.3 fails to HTML-escape the data-subtype attribute when generating gutter-button markup (app/src/protyle/gutter/button.ts, assigned via innerHTML in app/src/protyle/gutter/index.ts) from content pasted as plain-text Markdown containing a Kramdown inline attribute list (IAL). Because the shared Lute renderer parses Kramdown IAL from text/plain input, an attacker-supplied Markdown snippet using entity-encoded quotes in data-subtype breaks out of the attribute value when the gutter markup is re-parsed by the browser, injecting additional attributes such as autofocus and onfocus. If a victim pastes the crafted Markdown and the affected gutter control receives focus, the injected handler executes; in the Electron desktop application, where the main BrowserWindow enables Node integration and disables context isolation, this results in JavaScript execution with renderer Node.js privileges (remote code execution). Fixed in v3.8.4.

CVSS v3
8.8
EG Score
8.8HIGHhigh confidence
EG Risk
40
EG Risk 40/100CISA 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
Severity88% × 45%
Exploitation0% × 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
38th
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 none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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 26, 2026

Last Modified

September 28, 2026

Advisory Details (2)

Auto-updated Sep 26, 2026
🔬 Proof of concept available. Patch available. Sources: github.
generic

SiYuan before v3.8.4 Cross-Site Scripting via Kramdown IAL | Advisories | VulnCheck

https://www.vulncheck.com/advisories/siyuan-before-3.8.4-cross-site-scripting-via-kramdown-ial
github Patch Available🟡 PoC Available

Plain-text Kramdown IAL paste causes gutter attribute injection and desktop RCE · Advisory · siyuan-note/siyuan · GitHub

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-2cmm-9x9j-rvff

Vendor Advisories for CVE-2026-100639(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 31× in last 7d / 36× 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 10:37 UTCGHSA enrichment
  2. 2026-10-03 22:16 UTCEG score recompute
  3. 2026-10-03 22:16 UTCGHSA enrichment
  4. 2026-10-03 14:25 UTCEPSS rescore
  5. 2026-10-03 09:58 UTCGHSA enrichment
  6. 2026-10-02 21:40 UTCEG score recompute
  7. 2026-10-02 21:40 UTCGHSA enrichment
  8. 2026-10-02 09:24 UTCGHSA enrichment
  9. 2026-10-01 21:08 UTCEG score recompute
  10. 2026-10-01 21:08 UTCGHSA enrichment
  11. 2026-10-01 19:49 UTCEPSS rescore
  12. 2026-10-01 08:52 UTCGHSA enrichment
  13. 2026-09-30 20:36 UTCEG score recompute
  14. 2026-09-30 20:36 UTCGHSA enrichment
  15. 2026-09-30 15:02 UTCEPSS rescore
  16. 2026-09-30 08:21 UTCGHSA enrichment
  17. 2026-09-29 20:03 UTCEG score recompute
  18. 2026-09-29 20:03 UTCGHSA enrichment
  19. 2026-09-29 15:20 UTCEPSS rescore
  20. 2026-09-29 07:47 UTCEG score recompute
  21. 2026-09-29 07:47 UTCGHSA enrichment
  22. 2026-09-28 19:32 UTCEG score recompute
  23. 2026-09-28 19:31 UTCGHSA enrichment
  24. 2026-09-28 19:02 UTCEG score recompute
  25. 2026-09-28 19:02 UTCGHSA enrichment
Show 11 more
  1. 2026-09-28 15:40 UTCEG score recompute
  2. 2026-09-28 15:40 UTCGHSA enrichment
  3. 2026-09-28 13:50 UTCEPSS rescore
  4. 2026-09-28 03:23 UTCGHSA enrichment
  5. 2026-09-27 15:08 UTCEG score recompute
  6. 2026-09-27 15:07 UTCGHSA enrichment
  7. 2026-09-27 02:51 UTCEG score recompute
  8. 2026-09-27 02:51 UTCGHSA enrichment
  9. 2026-09-26 14:34 UTCEG score recompute
  10. 2026-09-26 13:40 UTCEG score recompute
  11. 2026-09-26 13:30 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-100639?
CVE-2026-100639 is a high vulnerability published on September 26, 2026. SiYuan v3.8.3 fails to HTML-escape the data-subtype attribute when generating gutter-button markup (app/src/protyle/gutter/button.ts, assigned via innerHTML in app/src/protyle/gutter/index.ts) from content pasted as plain-text Markdown containing a Kramdown inline attribute list (IAL). Because the…
When was CVE-2026-100639 disclosed?
CVE-2026-100639 was first published on September 26, 2026, with the most recent update on September 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-100639 actively exploited?
CVE-2026-100639 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (38th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-100639?
CVE-2026-100639 has a CVSS base score of 8.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-100639?
A fix for CVE-2026-100639 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-100639 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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