Description

SiYuan versions before 3.7.4 contain a cross-site WebSocket hijacking vulnerability in the admin-only /ws/network/proxy endpoint that explicitly disables origin validation by setting CheckOrigin to unconditionally return true. Attackers can craft malicious webpages that establish WebSocket connections to this endpoint and direct the SiYuan kernel process to proxy arbitrary network traffic to attacker-chosen targets, enabling authenticated network pivoting through the victim's machine.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.2",
  "pubDate": "2026-08-17T11:16:40.453Z",
  "pubdate": "2026-08-17T11:16:40.453Z",
  "executiveSummary": "SiYuan versions prior to 3.7.4 contain a cross-site WebSocket hijacking vulnerability residing in the admin-only /ws/network/proxy endpoint. The vulnerability stems from the explicit misconfiguration of the CheckOrigin function to unconditionally return true, thereby disabling origin validation for incoming WebSocket upgrade requests. This security flaw enables remote attackers to exploit authenticated victim sessions by hosting malicious webpages that successfully establish unauthorized WebSocket connections to the local or remote SiYuan kernel process.\nUpon successful exploitation, an attacker can leverage the compromised WebSocket channel to direct the SiYuan kernel to proxy arbitrary network traffic to attacker-chosen targets. This grants the attacker authenticated network pivoting capabilities through the victim's machine, potentially exposing internal network resources and services that are otherwise inaccessible from the external internet. The risk implications are severe, as the application executes privileged proxy actions on behalf of an authenticated administrator without verifying the provenance of the connection origin.\nExploitation requires the victim to visit a malicious webpage while maintaining an active administrative session with the SiYuan application, fulfilling the authentication requirement inherent to the targeted endpoint. The vulnerability directly impacts SiYuan instances running vulnerable versions below 3.7.4, necessitating immediate remediation to restore proper origin validation controls.",
  "technicalDetails": "The vulnerability is classified as a cross-site WebSocket hijacking (CSWSH) flaw affecting the SiYuan kernel process. The vulnerable component is the /ws/network/proxy endpoint, which is intended exclusively for administrative use. The root cause of the vulnerability lies in the improper implementation of the WebSocket handshake validation mechanism, specifically where the CheckOrigin function is hardcoded or configured to unconditionally return true. By bypassing origin validation, the endpoint accepts WebSocket upgrade requests originating from arbitrary, untrusted domains.\nThe attack flow proceeds as follows: an attacker crafts a malicious webpage embedded with JavaScript designed to initiate a WebSocket connection to the victim's SiYuan instance at the /ws/network/proxy endpoint. Because the application fails to validate the HTTP Origin header during the WebSocket handshake due to the unconditional CheckOrigin return value, the browser successfully establishes the persistent bidirectional communication channel. Once the connection is open, the malicious script sends specially crafted JSON or binary payloads over the WebSocket to instruct the SiYuan kernel to proxy arbitrary network traffic.\nThrough this proxying mechanism, the attacker achieves authenticated network pivoting. The SiYuan process acts as an intermediary, forwarding requests to internal services, local network segments, or external targets specified by the attacker, and returning the responses through the WebSocket channel. This effectively circumvents network perimeter controls, firewalls, and network address translation (NAT) boundaries by utilizing the victim's host and authenticated application context as a relay node.\nThe affected versions include all SiYuan releases prior to 3.7.4. Authentication and administrative privileges are implicitly required via the victim's active session, as the browser automatically includes session cookies or authentication tokens during the cross-origin WebSocket handshake request. Network exposure involves the administrative interface of the SiYuan kernel, which may be exposed locally or remotely depending on the deployment configuration."
}