Horizon Alert
Summary of the vulnerability and why it matters
This advisory concerns a critical vulnerability in SiYuan software related to its POST /mcp kernel endpoint. A flaw in authorization checks allows unauthenticated remote attackers to gain full administrator control of the system by exploiting the file tool and potentially planting malicious plugins.
- Unauthenticated access to administrator functions.
- Allows full system takeover.
- Confirm relevance and exposure to SiYuan.
Attack Path
How an attacker could exploit the issue
A remote attacker could exploit a missing authorization flaw in the SiYuan Publish server's POST /mcp endpoint to gain administrative control. This is possible when the server is configured for anonymous publishing, allowing unauthenticated requests to bypass proper role checks. The attacker can then extract sensitive credentials, manipulate files, and deploy malicious plugins, ultimately leading to full system takeover upon the next desktop application launch.
- Anonymous publishing enabled on Publish server.
- POST /mcp endpoint triggered remotely.
- Administrator takeover via plugin execution.
Live Threat
Current exploitation, exposure, and threat context
When the Publish server is enabled in anonymous mode, this vulnerability could allow an unauthenticated remote attacker to gain administrative control over the SiYuan workspace. This is achieved by exploiting a missing authorization check in the kernel's POST /mcp endpoint, which exposes various file management tools. The attacker could potentially read sensitive configuration details, write arbitrary files, and install a malicious plugin that executes with elevated privileges upon the next desktop launch.
- Workspace files and configuration data.
- Through anonymous, open Publish server access.
- Complete administrator takeover of the application.
Operational Fix
Recommended remediation, mitigation, and detection steps
The SiYuan Publish server, when enabled anonymously, presents a critical risk of administrator takeover by allowing unauthenticated remote attackers to execute arbitrary code. Application owners and platform teams are likely responsible for identifying and securing this component. The immediate priority is to locate all instances of the affected technology, verify their exposure to anonymous access, and confirm ownership to plan remediation.
- Application owners should prioritize this issue.
- Verify anonymous Publish server access status.
- Plan remediation based on identified risk.
