CVE-2026-74800: SiYuan before v3.7.4 Stored XSS via assets endpoint

Severity: critical (CVSS 9.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-17 · updated 2026-08-26
Weakness: CWE-79

Description

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.

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-mjf3-jwmf-r6wf
https://www.vulncheck.com/advisories/siyuan-before-stored-xss-via-assets-endpoint

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