CVE-2026-85693 in chatbot-ui
Summary
by MITRE • 09/04/2026
Chatbot UI contains an authorization bypass vulnerability in the retrieval endpoint that allows authenticated attackers to access private file content belonging to other users by supplying arbitrary file UUIDs. The endpoint uses a service-role Supabase client that bypasses row-level security and fails to validate file ownership, enabling attackers to retrieve indexed content chunks from victim files through crafted POST requests.
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Analysis
by VulDB Data Team • 09/04/2026
The identified vulnerability represents a critical authorization bypass within the chatbot user interface, specifically targeting the retrieval endpoint responsible for fetching document fragments or context chunks used in conversational AI responses. This flaw stems from an improper implementation of access control mechanisms where the application fails to enforce proper ownership verification on sensitive data resources. The core technical issue lies in the backend service architecture which utilizes a Supabase client configured with elevated, service-role privileges rather than user-specific credentials for this specific operation. By operating under these administrative or high-privilege context settings, the database layer effectively bypasses Row-Level Security policies that are typically designed to restrict data access based on user identity and ownership attributes. Consequently, the application logic does not perform any validation checks to ensure that the requesting authenticated user is the legitimate owner of the file identified by the provided UUID.
From a technical perspective, this vulnerability allows an attacker who has successfully authenticated to the chatbot system to manipulate HTTP POST requests containing arbitrary file identifiers. Instead of being limited to accessing only those documents explicitly shared with or owned by their account, the attacker can iterate through known or guessed Universally Unique Identifiers associated with other users' private files. Because the retrieval endpoint does not cross-reference the provided UUID against a database table mapping document ownership to user IDs before executing the query, it returns the indexed content chunks regardless of who created them. This behavior effectively neutralizes the intended isolation boundaries between different tenant or user contexts within the multi-tenant architecture, leading to a complete breakdown in data confidentiality for stored documents processed by the chatbot system.
The operational impact of this vulnerability is severe, as it facilitates unauthorized access to proprietary information, personal identifiable information, and other sensitive content uploaded by victims into the platform. Attackers can systematically enumerate file UUIDs or exploit predictable identifier patterns to harvest large volumes of private data without detection from standard audit logs that might only record successful retrievals rather than invalid authorization attempts if logging is not granular enough. This scenario aligns directly with CWE-284, which describes Improper Access Control, and specifically maps to the MITRE ATT&CK technique T1078, Valid Accounts, as it leverages legitimate authentication credentials to perform unauthorized actions that are outside the scope of normal user permissions. The ability to exfiltrate indexed content chunks also poses a significant risk for downstream AI applications, potentially allowing attackers to inject malicious context or extract trade secrets by reading training data or internal documentation stored in vector databases.
To mitigate this vulnerability, immediate remediation efforts must focus on enforcing strict object-level authorization checks at the application layer before any database queries are executed. The service-role Supabase client should not be used for user-facing retrieval operations that involve sensitive private data; instead, the system must utilize a standard authenticated client context or explicitly pass the current user's identity to enforce Row-Level Security policies correctly. Developers must implement explicit validation logic that verifies the requesting user ID matches the owner_id field associated with the requested file UUID in the database backend. Additionally, implementing comprehensive audit logging for all retrieval attempts involving private files can aid in detecting ongoing exploitation activities. Long-term architectural improvements should include adopting a principle of least privilege for service accounts and ensuring that all API endpoints undergo rigorous security testing to validate access control logic against various user roles and permission sets.