Trilium Notes CVE-2026-39310

Exploitation requires that the victim is running Trilium Desktop (the Electron build, not the server distribution) at version 0.102.1 or earlier, with the Clipper API listening on a network-reachable interface rather than localhost only, and that the attacker shares a routable network path to the victim's machine (same LAN, Wi-Fi segment, or VPN broadcast domain). No credentials, user interaction, CSRF token, or non-default configuration is needed - the auth bypass is the default behavior whenever Electron is detected. Limiting factors: pure server-mode Trilium deployments are not in scope of this bypass logic, and hosts that firewall the Clipper port or bind it to loopback are not reachable.

The CVSS 8.6 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L) is internally consistent with the description: network-reachable, no authentication, low complexity, with the dominant impact on integrity (note modification) and lesser confidentiality/availability impact. No EPSS score, KEV listing, or public POC was provided, so real-world exploitation pressure cannot be quantified from the supplied data - the practical risk is bounded by attacker network adjacency (corporate LAN, public Wi-Fi, or shared VPN segment) rather than internet-wide scanning, which lowers blast radius compared to a typical AV:N flaw. The handshake endpoint's clean fingerprint response makes mass-scanning trivial once an attacker is on-LAN, so for desktop users on untrusted networks this should be treated as a priority patch rather than a theoretical issue.

An attacker joins a corporate LAN or public Wi-Fi where a victim is running Trilium Desktop, runs nmap across high ports to find the Clipper listener (e.g. 37840), and hits the handshake endpoint, which responds with the Trilium app name and protocol version even without auth. The attacker then calls /api/clipper/notes to read existing notes or inject attacker-controlled content - for example a phishing lure or a payload that the victim later clicks - achieving data theft and a foothold for follow-on social engineering or local compromise.