What is CVE-2026-100640?

CVE-2026-100640 is a medium-severity vulnerability in Siyuan-Note Siyuan, classified under Information Disclosure. CVSS score: 4.7/10. Published 2026-09-26.

How severe is CVE-2026-100640?

Medium severity. CVSS v3 base score is 4.7 out of 10.

Information disclosure in Siyuan-Note Siyuan

CVE-2026-100640

SiYuan before v3.8.4 contains an authorization omission in the siyuan-get IPC handler that allows remote-kernel renderers to access native clipboard formats by invoking clipboardReadMathML, clipboardReadOffice, and clipboardReadWPS commands with matching plaintext. Attackers controlling remote renderer content can obtain MathML formulas, Office bytes, and WPS bytes from local clipboard during user-mediated paste operations.

Vulnerability class: Information Disclosure

Published 2026-09-26 · last modified 2026-09-26.

CVSS v3 metric

CVSS v3 base score 4.7 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Siyuan-Note Siyuan

Weakness classification (CWE)

CWE-200 — Information Disclosure

References

github.com/siyuan-note/siyuan/security/advisories/GHSA-mjmm-hgmc-m7qf (vendor-advisory)
www.vulncheck.com/advisories/siyuan-before-3.8.4-clipboard-data-disclosure-via-… (third-party-advisory)

Frequently asked questions

What is CVE-2026-100640?: CVE-2026-100640 is a medium-severity vulnerability in Siyuan-Note Siyuan, classified under Information Disclosure. CVSS score: 4.7/10. Published 2026-09-26.
How severe is CVE-2026-100640?: Medium severity. CVSS v3 base score is 4.7 out of 10.