Description

SiYuan versions before v3.7.4 contain an authentication bypass vulnerability in the WebSocket endpoint caused by differential parsing of query parameters between authentication exemption and session quarantine checks. Unauthenticated attackers can craft a malicious WebSocket URI with duplicated query parameters to bypass access auth code validation and receive the live kernel event stream including document identifiers, titles, and operation logs.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.5",
  "pubDate": "2026-08-15T22:16:55.290Z",
  "pubdate": "2026-08-15T22:16:55.290Z",
  "executiveSummary": "SiYuan versions prior to v3.7.4 are affected by an authentication bypass vulnerability located within the WebSocket endpoint. This security flaw stems from differential parsing of query parameters between the authentication exemption mechanism and session quarantine checks.\nAn unauthenticated, remote attacker can exploit this discrepancy by crafting a malicious WebSocket URI containing duplicated query parameters. Successful exploitation allows the attacker to completely bypass access authorization code validation, directly violating the core security boundary of the application.\nThe primary impact of this vulnerability is the unauthorized exposure of the live kernel event stream. By leveraging this flaw, malicious actors gain access to sensitive internal application data, including document identifiers, document titles, and real-time operation logs.\nThe attack requires network access to the target SiYuan WebSocket endpoint and does not necessitate any prior authentication, valid user credentials, or administrative privileges. Consequently, the risk implication is significant for exposed instances, as passive or active monitoring of the kernel event stream can lead to severe information disclosure regarding user activities and document structures within the knowledge management system.",
  "technicalDetails": "The vulnerability resides in the WebSocket endpoint of SiYuan versions prior to v3.7.4. The root cause of the flaw is inconsistent query parameter parsing logic implemented across different internal security layers, specifically during the handling of authentication exemption routines versus session quarantine checks.\nWhen a client initiates a WebSocket connection, the application inspects the provided query parameters to determine whether the request qualifies for authentication exemption or if it requires active session validation. Due to differential parsing behavior, an attacker can supply duplicated query parameters within the WebSocket URI. This structural anomaly causes the authentication exemption validation check to parse the parameters in a manner that falsely authorizes the connection, while the subsequent session quarantine or core routing logic processes the stream differently, successfully granting access to restricted execution paths without validating the required access auth code.\nThe attack flow proceeds as follows: First, the unauthenticated attacker crafts a malicious WebSocket URI targeting the vulnerable endpoint, embedding specifically manipulated, duplicated query parameters designed to trigger the parser differential. Second, the attacker initiates the WebSocket handshake using this crafted URI. Third, the application's authentication exemption mechanism evaluates the request, encounters the parsing discrepancy, and incorrectly bypasses the access auth code validation requirement. Fourth, the handshake completes successfully, establishing an active WebSocket session for the unauthenticated connection. Finally, the server begins streaming the live kernel event stream to the attacker.\nThe vulnerable component is the WebSocket endpoint routing and authentication middleware of SiYuan. The affected versions include all releases prior to v3.7.4. Network exposure is required, as the endpoint must be reachable by the attacker over the network. Authentication and privilege requirements are entirely absent, allowing unauthenticated threat actors to execute the attack. Payload behavior involves maintaining the unauthorized WebSocket connection to harvest sensitive data. The post-exploitation impact includes the continuous leakage of sensitive operational telemetry, such as document identifiers, document titles, and detailed operation logs, severely compromising the confidentiality of the SiYuan instance."
}