In decolua 9router versions before 0.5.2, the application relies on the client-supplied Host header to determine if a /v1 LLM proxy request is local. This design flaw allows a remote unauthenticated attacker to spoof the Host header as 'localhost' and bypass API-key authentication. Consequently, the attacker can access the /v1 proxy endpoint, which in the default configuration exposes upstream provider calls using stored credentials. Additionally, the /v1/search endpoint with the searxng provider_options.baseUrl parameter can be abused to perform server-side requests to internal or cloud metadata hosts. The vulnerability is addressed by updating to version 0.5.2.

The vulnerability enables remote unauthenticated attackers to bypass authentication controls and access sensitive API endpoints. This can lead to unauthorized use of stored provider credentials for upstream calls and server-side request forgery to internal or cloud metadata services. The confidentiality of sensitive data is at high risk, while integrity impact is low and availability is not affected.

Upgrade decolua 9router to version 0.5.2 or later, where this authentication bypass vulnerability is fixed. No other mitigation or temporary workaround is indicated in the available data.