CVE-2026-39311

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.

CVSS v3.1 Score

6.8

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:C/C:L/I:L/A:H

EPSS — Exploit Prediction

0.0012

Probability of exploitation

0.30%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)

CWE-94 CWE-94

References

Other References

https://github.com/TriliumNext/Trilium/releases/tag/v0.102.2 https://github.com/TriliumNext/Trilium/security/advisories/GHSA-p837-cxw3-m964 https://github.com/TriliumNext/Trilium/security/advisories/GHSA-p837-cxw3-m964

Frequently Asked Questions

What is CVE-2026-39311? +

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. It has a CVSS v3.1 base score of 6.8 (MEDIUM).

How severe is CVE-2026-39311? +

CVE-2026-39311 has a CVSS v3.1 score of 6.8 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0012, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-39311? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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