CVE-2026-23852: SiYuan vulnerable to Stored XSS / RCE via `setBlockAttrs` icon attribute

Severity: critical (CVSS 9.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-01-19 · updated 2026-06-17
Weakness: CWE-94

Description

SiYuan is a personal knowledge management system. Versions prior to 3.5.4 have a stored Cross-Site Scripting (XSS) vulnerability that allows an attacker to inject arbitrary HTML attributes into the `icon` attribute of a block via the `/api/attr/setBlockAttrs` API. The payload is later rendered in the dynamic icon feature in an unsanitized context, leading to stored XSS and, in the desktop environment, potential remote code execution (RCE). This issue bypasses the previous fix for issue `#15970` (XSS → RCE via dynamic icons). Version 3.5.4 contains an updated fix.

Affected products

siyuan-note siyuan: before 3.5.4 — fixed in 3.5.4

How to fix

Upgrade to a fixed version: siyuan-note siyuan 3.5.4. Check the vendor advisory for mitigations.

References

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