CVE-2026-39311 Trilium Notes: Stored XSS Leads to Unauthorized Remote Code Execution (RCE) via Unsanitized SVG Attachments
Attackers can achieve remote code execution by tricking users into viewing unsanitized SVG attachments, exploiting disabled CSP and exposed APIs.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-39311?
CVE-2026-39311 is a medium-severity cross-site scripting vulnerability in TriliumNext Trilium, published on 20 May 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Official description
Trilium Notes is a cross-platform, hierarchical note taking application focused on building large personal knowledge bases. Versions 0.102.1 and prior contain a critical security flaw where lack of SVG sanitization combined with a disabled Content Security Policy (CSP) and a publicly reachable backend execution API results in an unauthenticated Remote Code Execution (RCE). The vulnerability arises from an insecure-by-design architecture: Trilium serves SVG attachments with the image/svg+xml MIME type without any sanitization, and it explicitly disables Helmet's Content Security Policy middleware, removing the primary defense against script execution in served assets. Because the malicious SVG runs under the Same-Origin Policy, it can issue a fetch('/') to extract the csrfToken from the document body. With that token, it can send a signed request to /api/script/exec to execute arbitrary Node.js code on the server. An attacker can compromise the entire server instance simply by tricking an authenticated user into viewing a shared SVG attachment. The issue has been fixed in version 0.102.2.
Which versions are affected by CVE-2026-39311?
How do I fix CVE-2026-39311?
No fix has been published for CVE-2026-39311 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-2026-39311 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39311 exists.
Sources
Also known as GHSA-p837-cxw3-m964.