HIGH

CVE-2026-100639

CVSS v3

8.8

HIGH

EPSS Score

0.5 %

exploit probability, as of 2026-09-28

CISA KEV

known exploited

Exploitation

—

SSVC status

Description

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 marku

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Published: 2026-09-26
Last Modified: 2026-09-26

Frequently asked questions

What is CVE-2026-100639?

Is CVE-2026-100639 actively exploited?

Active exploitation of CVE-2026-100639 has not been confirmed. Its EPSS score was 0.5% on 2026-09-28, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-100639?

CVE-2026-100639 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

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