CVE-2026-42090 Notesnook: RCE via stored XSS in note export rendering

Critical 9.6 Published 4 May 2026 Updated 5 May 2026

Attackers can achieve remote code execution in the Notesnook desktop app via stored XSS in note exports due to unsafe HTML rendering and Electron configuration.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2026-42090?

CVE-2026-42090 is a critical cross-site scripting vulnerability in streetwriters notesnook, published on 4 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

Notesnook is a note-taking app focused on user privacy & ease of use. Prior to Notesnook Web/Desktop version 3.3.15 and prior to Notesnook iOS/Android version 3.3.20, a stored XSS vulnerability in the note export flow can be escalated to remote code execution in the desktop app. The root cause is that exported note fields such as title, headline, and content are inserted into the generated HTML template without HTML escaping. When the note is later exported to PDF, Notesnook renders that HTML into a same-origin, unsandboxed iframe using iframe.srcdoc = .... Injected script executes in the Notesnook origin. In the desktop app, this becomes RCE because Electron is configured with nodeIntegration: true and contextIsolation: false. This issue has been patched in Notesnook Web/Desktop version 3.3.15 and Notesnook iOS/Android version 3.3.20.

Weakness: CWE-94, CWE-79

Which versions are affected by CVE-2026-42090?

It affects 2 products.

Products include Streetwriters Notesnook Desktop, Streetwriters Notesnook Mobile.

How do I fix CVE-2026-42090?

No fix has been published for CVE-2026-42090 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-2026-42090 being exploited?

There is no known exploitation of CVE-2026-42090 in the wild and no public exploit code.

Sources

Also known as GHSA-fjm8-jg78-89h4.