CVE-2026-74802 describes a cross-site WebSocket hijacking vulnerability in SiYuan versions prior to 3.7.4. The vulnerability exists because the /ws/network/proxy admin-only endpoint disables origin validation by setting CheckOrigin to always return true. This flaw allows attackers to craft malicious webpages that establish WebSocket connections to this endpoint, causing the SiYuan kernel process to proxy arbitrary network traffic to attacker-controlled targets. The attack requires victim authentication and enables network pivoting through the victim's machine.

An attacker can leverage this vulnerability to proxy arbitrary network traffic through an authenticated victim's machine, effectively enabling network pivoting. This can facilitate further attacks within the victim's network environment. The vulnerability has a CVSS 4.0 base score of 7.1 (high severity), indicating significant risk if exploited.

A fix is available in SiYuan version 3.7.4. Users should upgrade to version 3.7.4 or later to remediate this vulnerability. No additional mitigation guidance is provided or required beyond applying the official update.