CVE-2026-33203

Received Received - Intake

WebSocket Unauthenticated Access and DoS in SiYuan Kernel

Publication date: 2026-03-20

Last updated on: 2026-03-23

Assigner: GitHub, Inc.

Description

SiYuan is a personal knowledge management system. Prior to version 3.6.2, the SiYuan kernel WebSocket server accepts unauthenticated connections when a specific "auth keepalive" query parameter is present. After connection, incoming messages are parsed using unchecked type assertions on attacker-controlled JSON. A remote attacker can send malformed messages that trigger a runtime panic, potentially crashing the kernel process and causing denial of service. Version 3.6.2 fixes the issue.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-03-20

Last Modified

2026-03-23

Generated

2026-07-06

AI Q&A

2026-03-21

EPSS Evaluated

2026-07-05

NVD

CVE-2026-33203

Affected Vendors & Products

Vendor	Product	Version / Range
b3log	siyuan	to 3.6.2 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-306	The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
CWE-248	An exception is thrown from a function, but it is not caught.

Attack-Flow Graph

Executive Summary

This vulnerability exists in the SiYuan personal knowledge management system prior to version 3.6.2. The kernel WebSocket server accepts unauthenticated connections if a specific "auth keepalive" query parameter is present. Once connected, the server parses incoming messages using unchecked type assertions on attacker-controlled JSON data. A remote attacker can exploit this by sending malformed messages that cause a runtime panic, potentially crashing the kernel process.

Impact Analysis

The primary impact of this vulnerability is a denial of service condition. An attacker can remotely crash the SiYuan kernel process by sending specially crafted malformed messages, causing the system to become unavailable or unstable.

Compliance Impact

I don't know

Detection Guidance

I don't know

Mitigation Strategies

To mitigate this vulnerability, you should upgrade SiYuan to version 3.6.2 or later, as this version fixes the issue where the kernel WebSocket server accepts unauthenticated connections and prevents denial of service caused by malformed messages.

Hi! I’m here to help you understand CVE-2026-33203. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70