CVE-2026-74902: SiYuan before v3.7.4 XSS-to-RCE via malicious filename upload

Severity: high (CVSS 8.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-18 · updated 2026-10-22
Weakness: CWE-79

Description

SiYuan before v3.7.4 contains a cross-site scripting vulnerability in the file upload validation flow that fails to escape filenames before inserting them into HTML via insertAdjacentHTML. Attackers can craft a malicious filename containing script payloads that execute with full OS command access when a user drags, drops, or pastes the file into the editor.

Affected products

siyuan-note siyuan: before 3.7.4 — fixed in 3.7.4

How to fix

Upgrade to a fixed version: siyuan-note siyuan 3.7.4. Check the vendor advisory for mitigations.

References

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-jf56-jrhq-j2qp
https://www.vulncheck.com/advisories/siyuan-before-xss-to-rce-via-malicious-filename-upload

Get alerted when CVE-2026-74902 or the next vulnerability affects your stack