CVE-2026-71203 in changedetection.io
Summary
by MITRE • 08/05/2026
changedetection.io's REST API resources are protected by an @auth.check_token decorator validating the caller's x-api-key header, except the Spec resource registered at /api/v1/full-spec (changedetectionio/api/Spec.py), whose get() method carries neither @auth.check_token nor @validate_openapi_request. An unauthenticated client can retrieve the full merged OpenAPI schema (all endpoint paths, parameters, and registered processor plugins) even when API access control is enabled and every sibling /api/v1/* route correctly requires the key.
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Analysis
by VulDB Data Team • 08/05/2026
This vulnerability represents a critical authorization bypass in changedetection.io's REST API implementation where the Spec resource at /api/v1/full-spec fails to enforce authentication requirements that protect all other API endpoints. The issue stems from the inconsistent application of security decorators across the API surface, specifically the absence of auth.check_token and validate_openapi_request decorators on the Spec resource's get() method. While all sibling routes correctly validate the x-api-key header through the @auth.check_token decorator, this particular endpoint remains accessible to unauthenticated clients regardless of whether API access control is enabled.
The technical flaw resides in the improper security configuration where the OpenAPI specification endpoint becomes a vector for information disclosure without proper authentication controls. This represents a violation of the principle of least privilege and demonstrates a classic security misconfiguration pattern that allows unauthorized access to sensitive system metadata. The vulnerability enables attackers to obtain the complete merged OpenAPI schema which includes all registered endpoint paths, parameters, and processor plugins, effectively providing them with comprehensive knowledge of the application's API structure and capabilities.
From an operational perspective, this authorization bypass exposes critical infrastructure information that could facilitate further attacks against the changedetection.io application. An attacker who discovers this endpoint could use the retrieved OpenAPI schema to understand all available API endpoints, their parameters, and expected data formats, potentially enabling them to craft more sophisticated attacks or identify additional vulnerabilities within the system. The exposure of registered processor plugins particularly concerns security practitioners as it reveals the underlying functionality and potential attack surfaces that may not be immediately obvious through normal application interaction.
The impact of this vulnerability aligns with CWE-285 (Improper Authorization) and can be categorized under ATT&CK technique T1594 (Reconnaissance) where adversaries gather information about the target environment. Organizations using changedetection.io may experience increased risk of targeted attacks once attackers obtain detailed knowledge of the API structure, potentially leading to exploitation of other vulnerabilities or unauthorized access to monitored web services. The remediation requires implementing proper authentication decorators on the Spec resource and ensuring consistent security controls across all API endpoints.
Security best practices dictate that all API resources should maintain uniform protection mechanisms regardless of their functional purpose. This incident highlights the importance of comprehensive security testing including endpoint enumeration and access control verification, particularly for applications that expose OpenAPI specifications publicly. The vulnerability demonstrates how a single missing decorator can compromise the entire security posture of an application's API layer, emphasizing the need for automated security scanning tools to identify such misconfigurations during development and deployment phases. Organizations should implement continuous monitoring of API endpoint access patterns and ensure that all resources requiring authentication consistently enforce those requirements through proper decorator implementation and code review processes.
The exposure of processor plugins through this vulnerability could enable attackers to understand how different web scraping or notification mechanisms work within the system, potentially allowing them to craft targeted attacks against specific plugin implementations. This information disclosure represents a significant risk for applications handling sensitive monitoring data where the API endpoints may reveal details about monitored services and their configurations. Proper implementation should ensure that even informational endpoints maintain appropriate access controls to prevent unauthorized enumeration of system capabilities and potential attack vectors.