What is CVE-2026-74800?

CVE-2026-74800 is a critical-severity vulnerability in Siyuan-Note Siyuan, classified under Cross-site Scripting. CVSS score: 9.0/10. Published 2026-08-17.

How severe is CVE-2026-74800?

Critical severity. CVSS v3 base score is 9.0 out of 10.

XSS in Siyuan-Note Siyuan

CVE-2026-74800

SiYuan before v3.7.4 fails to set Content-Disposition and X-Content-Type-Options headers when serving arbitrary file assets, allowing stored cross-site scripting attacks. Authenticated attackers can upload HTML files as assets and execute scripts with full kernel API access when the workspace owner opens the asset link.

Vulnerability class: XSS (Cross-Site Scripting)

CVSS v3 metric

CVSS v3 base score 9.0 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H.

Affected products

Siyuan-note Siyuan — versions 0, 3.7.4

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

disclosure@vulncheck.com (vendor-advisory)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-74800?: CVE-2026-74800 is a critical-severity vulnerability in Siyuan-Note Siyuan, classified under Cross-site Scripting. CVSS score: 9.0/10. Published 2026-08-17.
How severe is CVE-2026-74800?: Critical severity. CVSS v3 base score is 9.0 out of 10.