External risk intelligence

SiYuan Unauthenticated Debug Endpoint Information Disclosure.

CVE advisorySeverity: CRITICAL (CVSS 9.2)

CVE-2026-74799

SiYuan is a personal knowledge management application. While it can be self-hosted and network-accessible, it is typically used as a local or private service rather than a public-facing internet edge gateway or web application. Debug endpoints may be reachable if the instance is improperly exposed to the internet, but public exposure is not the default or intended design for this product role.

Halo Surface Signal: 3 out of 5 — possibly public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This vulnerability involves certain versions of SiYuan that, under specific configurations, expose unauthenticated debug endpoints. These endpoints could allow unauthorized access to sensitive in-memory data, such as access codes and API keys, if the application is improperly exposed. The primary concern is to verify if your SiYuan instances are configured in a way that could make these sensitive endpoints accessible externally.

Unauthenticated debug endpoints can leak secrets.
Leadership should remember potential data exposure risks.
Confirm relevance and exposure of sensitive data.

Attack Path

How an attacker could exploit the issue

An attacker can access unauthenticated debug endpoints if the SiYuan application is not configured with its production mode. This exposure allows unauthorized individuals to view sensitive information, potentially leading to the compromise of access credentials and API keys.

No authentication required for endpoints.
Access to debug endpoints reveals secrets.
Risk of credential and API key theft.

Live Threat

Current exploitation, exposure, and threat context

When the SiYuan `--mode` flag is not set to `prod`, unauthenticated debug endpoints, including heap and goroutine dumps, can be exposed. This could allow attackers to extract sensitive in-memory data such as AccessAuthCode and AI provider API keys.

In-memory secrets could be exposed.
Unauthenticated debug endpoints can be accessed.
Sensitive secrets may be compromised.

Operational Fix

Recommended remediation, mitigation, and detection steps

The SiYuan application's unauthenticated debug endpoints, particularly when the `--mode` flag is not set to `prod`, present a critical risk. Application owners or platform teams responsible for SiYuan instances should first confirm the scope of affected deployments and their network exposure. Understanding whether these instances are reachable externally or host business-critical data is paramount before planning any remediation or mitigation efforts.

Ownership: Application or Platform Engineering teams.
Verify first: Network reachability and data criticality.
Action: Assess exposure and plan remediation.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is SiYuan?

SiYuan is a personal knowledge management tool designed to help users organize notes, tasks, and data. It supports self-hosting, allowing users to run the application on their own infrastructure or private servers for local document management and collaborative editing.

How does CVE-2026-74799 impact SiYuan?

This vulnerability involves an information disclosure weakness, categorized as CWE-215. When the software is not explicitly configured for production mode, it leaves debugging interfaces accessible without authentication. These interfaces, intended for developer diagnostics, inadvertently allow unauthorized parties to view memory contents.

When is an instance vulnerable to this debug endpoint issue?

A SiYuan instance is only affected when the command-line flag --mode is set to anything other than exactly "prod". If the application is running in a default or development-oriented state, the debug endpoints remain active and reachable. The vulnerability does not exist if the software is correctly locked down in production mode.

Is my SiYuan instance at risk?

Halo Surface Signal notes that SiYuan is typically a private service, not an internet-facing gateway. Your risk increases if you have manually configured your instance to be reachable over the public internet. Instances restricted to local networks or private segments have a significantly lower chance of being accessed by unauthorized remote parties.

What steps should I take to address this vulnerability?

Start by identifying all deployed SiYuan instances to check their current configuration. For any instance not set to --mode=prod, update the deployment settings to enforce production mode. You should also evaluate your network access policies to ensure that sensitive knowledge management services are not unnecessarily exposed to public networks.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.