GHSA-7r7x-gjvr-448g Open WebUI: Upload `metadata.knowledge_id` bypasses the knowledge-base write-access check (read-only users can add files to KB)
Open WebUI upload metadata can add files to knowledge bases without write permissionSummaryOpen WebUI's file upload background processing trusts the client-supplied `metadata.knowledge_id` value and inserts a `knowledge_file` association before validating that the uploading user has write access to the target knowledge base.A verified user with only read access to a knowledge base can upload an arbitrary file and set `metadata={"knowledge_id":"<target knowledge id>"}`. The normal `/api/v1/knowledge/{id}/file/add` endpoint correctly requires knowledge-base write access, but the upload auto-link path bypasses that authorization check.The immediate result is unauthorized modification of the target knowledge base's file membership. The attached attacker-controlled file becomes visible through `/api/v1/knowledge/{id}/files`, and readers/owners of that knowledge base can retrieve the file through the normal file endpoints because file access is derived from `KnowledgeFile` membership.Affected VersionRepository: `open-webui/open-webui`Tested source commit: `02dc3e689ceac915a870b373318b99c029ddf603`Package version observed in `package.json`: `0.9.6`Package name: `open-webui`ImpactA read-only knowledge-base collaborator can perform a write operation against that knowledge base by attaching arbitrary uploaded files.Security impact:Unauthorized knowledge-base membership modification.Integrity impact on shared knowledge-base file listings.Attacker-controlled files become readable to other users who can read the target knowledge base.If an owner/admin later reprocesses or globally reindexes the knowledge base, the unauthorized file can be indexed into the knowledge collection, turning the membership bypass into RAG/content poisoning.This is not an unauthenticated issue. It requires a verified Open WebUI account and a valid target knowledge-base ID. The clearest exploit path is a user who legitimately has read access to a knowledge base but not write access.Source EvidenceThe normal single-file knowledge add endpoint checks write permission before processing or inserting the relationship:`backend/open_webui/routers/knowledge.py``add_file_to_knowledge_by_id`Lines 714-728 reject callers who are not owner, admin, or granted `write` access.Lines 750-766 then process and insert the file only after that authorization gate.The upload auto-link path does not perform the same check:`backend/open_webui/routers/files.py``process_uploaded_file`Lines 178-186 read `knowledge_id` from upload metadata and immediately call `Knowledges.add_file_to_knowledge_by_id(...)`.Lines 187-192 call `process_file(... collection_name=knowledge_id ...)` after the insert.The model method inserts the relationship without validating the caller's write access to the knowledge base:`backend/open_webui/models/knowledge.py``add_file_to_knowledge_by_id`Lines 646-677 create and commit a `KnowledgeFile` row for the supplied `knowledge_id`, `file_id`, and `user_id`.The later vector write check exists, but it runs too late:`backend/open_webui/routers/retrieval.py``process_file`Lines 1587-1592 call `_validate_collection_access(..., access_type='write')` when a collection is supplied.Because the unauthorized `KnowledgeFile` row is already committed before that check runs, the failed vector processing does not undo the knowledge-base file association. The upload code catches the exception at `backend/open_webui/routers/files.py` lines 194-195 and logs a warning while leaving the row in place.The unauthorized relationship affects file access decisions:`backend/open_webui/utils/access_control/files.py``has_access_to_file`Lines 41-53 grant file access when a file is associated with a knowledge base the user can access.So once the attacker's file is inserted into the target `KnowledgeFile` table, target knowledge-base readers/owners can see and fetch that file through normal knowledge/file routes.Reproduction StepsUse a local Open WebUI instance with two verified users:As user `owner`, create a knowledge base.Grant user `reader` read access to the knowledge base, but do not grant write access.As `reader`, confirm the normal add-file endpoint is blocked:Expected and observed behavior for the normal route: it rejects the request because `reader` lacks knowledge-base write access.As `reader`, upload a new file with the same target knowledge ID embedded in upload metadata:Observe that the upload request succeeds and returns the uploaded file record.As `owner`, request the knowledge-base files:Observe that `attacker-note.txt` appears in the target knowledge base even though `reader` did not have write access.As `owner`, request the file content:Observe that the file is retrievable because `has_access_to_file` derives access from the unauthorized knowledge-base membership.Expected BehaviorThe upload auto-link path should enforce the same authorization contract as `/api/v1/knowledge/{id}/file/add`:The target knowledge base must exist.The caller must be the knowledge owner, an admin, or have `write` access.The supplied `directory_id`, if present, must belong to the target knowledge base.The `KnowledgeFile` association should only be inserted after authorization and processing succeed.Actual Behavior`metadata.knowledge_id` causes `Knowledges.add_file_to_knowledge_by_id(...)` to insert a `KnowledgeFile` row before write authorization is checked. The later collection write validation can fail, but the unauthorized membership row remains committed.Suggested FixMove knowledge-base authorization before the insert in the upload auto-link path. The upload path should share the same write-access and directory validation logic used by the dedicated knowledge endpoints.One safe pattern:Load the target knowledge base.Require owner/admin/write access before calling `Knowledges.add_file_to_knowledge_by_id`.Validate that `directory_id`, if supplied, belongs to the same knowledge base.Run vector processing before inserting the membership row, or wrap processing plus insertion in a transaction/compensating cleanup so a denied or failed process cannot leave a stale unauthorized row.
CVSS v3.1 score: 4.3