CVE-2026-100641 SiYuan before v3.8.4 Stored XSS via Unescaped Flashcard Content
Stored XSS in SiYuan allows attackers to execute arbitrary code on the host via malicious flashcard content processed by the privileged Electron renderer.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-100641?
CVE-2026-100641 is a high-severity cross-site scripting vulnerability in siyuan-note siyuan, published on 26 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
SiYuan before v3.8.4 does not HTML-escape stored flashcard block content before interpolating it into the card-manager list markup. Block content returned by /api/riff/getRiffCards is inserted into a card item template in app/src/card/viewCards.ts and assigned to listElement.innerHTML, so content such as <img src=invalid onerror=...> becomes an executable event-handler attribute. Because the SiYuan desktop (Electron) main window is created with nodeIntegration enabled and contextIsolation disabled, an administrator who opens the card manager on a workspace containing attacker-supplied flashcard content (for example introduced through contribution or import) executes the attacker's script in a privileged renderer, which can lead to arbitrary code execution on the host. The affected endpoint remains behind authentication and administrator-role checks; this is an untrusted-content-to-privileged-renderer issue, not an authorization bypass.
Weakness: CWE-79
Which versions are affected by CVE-2026-100641?
How do I fix CVE-2026-100641?
No fix has been published for CVE-2026-100641 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-100641 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-100641 exists.
Sources
Also known as GHSA-2mmf-4xwm-55rm, GHSA-wvmc-29rv-83j2.