External risk intelligence

danmu_api Authentication Bypass via Default Token

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2026-116485

The vulnerability exists in an API application (danmu_api) and is reachable via POST requests to specific API endpoints (/api/env/set, /api/env/add, /api/env/del). APIs are commonly deployed as internet-facing services or web-accessible backends, making them reachable in typical real-world deployments.

Missing Authentication

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A security vulnerability in the danmu_api software allows attackers to bypass authentication and alter server configurations. This could lead to unauthorized control, redirection of network traffic, or service disruptions if default security settings are used and administrative tokens are not properly configured. The main concern is confirming relevance and exposure.

Unauthenticated attackers can change server settings.
Affects systems using default API security.
Confirm if this technology is in use.

Attack Path

How an attacker could exploit the issue

An attacker can bypass authentication by exploiting a vulnerability in the danmu_api, specifically when the default TOKEN is used and ADMIN_TOKEN is not set. By sending POST requests to certain API endpoints, an unauthenticated attacker can modify server configuration, potentially leading to denial of service, server-side request forgery, or unauthorized redeployment.

No authentication required for access.
Triggered by POST requests to env endpoints.
Allows unauthorized configuration changes.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an unauthenticated attacker to bypass authentication and modify server environment configurations. When the default TOKEN is in use and ADMIN_TOKEN is not set, an attacker could send POST requests to specific API endpoints to alter settings, potentially leading to unauthorized control, redirection of traffic, or unexpected system redeployments.

Server environment configuration.
Unauthenticated POST requests to API endpoints.
Unauthorized control and traffic redirection.

Operational Fix

Recommended remediation, mitigation, and detection steps

The danmu_api authentication bypass vulnerability, particularly when the default TOKEN is used, impacts application owners and potentially platform or infrastructure teams. The immediate priority is to identify all instances of danmu_api, assess their exposure (especially if internet-facing or handling sensitive configuration), and determine which systems are business-critical. Once confirmed, engage the accountable owner to plan remediation, prioritizing instances with default tokens and unconfigured ADMIN_TOKEN.

Application and platform teams own remediation.
Verify API exposure and default token usage.
Plan configuration changes and updates.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

Free EASM Trial See How Signal Works

Frequently asked questions

What is danmu_api?

danmu_api is an application designed to manage server environment settings and API communication. It acts as a backend service, often used to handle tasks like proxy configuration and service redeployment. Users rely on it to automate infrastructure adjustments through its provided API endpoints.

What does CWE-306 mean for CVE-2026-116485?

CWE-306 refers to a Missing Authentication for Critical Function vulnerability. In the context of CVE-2026-116485, it means the software fails to verify the identity of a user before allowing them to access sensitive commands. Because of this, an attacker can perform administrative actions—such as altering server configuration—without needing to provide valid credentials.

How can an attacker trigger this vulnerability?

An attacker can trigger this by sending a specially crafted POST request to specific environment-related API endpoints. The flaw only activates when the system is left in a vulnerable state: specifically, when the default TOKEN is still active and a custom ADMIN_TOKEN has not been set. If a strong, custom ADMIN_TOKEN is configured, these requests will not successfully bypass authentication.

How do I know if my system is at risk?

According to Halo Surface Signal, this vulnerability is particularly concerning because the affected endpoints are often exposed as internet-facing services. If your danmu_api instance is reachable from the public internet, it faces a higher likelihood of being targeted. You should prioritize checking any instances that provide external-facing API services.

What should I do first to secure my systems?

Start by identifying all deployed instances of danmu_api within your environment to confirm if you are using this technology. Verify that you have moved away from default security settings by ensuring a unique ADMIN_TOKEN is configured. If you are running a version earlier than 1.21.7, prepare to update to a patched version to resolve the underlying authentication flaw.

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.