VU#754548: Cinnamon's Kotaemon contains improper authorization checks in Kotaemon multi‑user chat handlers

Cinnamon's Kotaemon (all versions up to v0.12.0) multi‑user chat interface does not verify conversation ownership when loading a conversation. Any authenticated user can read, delete, rename, or overwrite another user’s conversation data by supplying the correct ID. This results in high‑impact confidentiality, integrity, and availability violations.

Cinnamon's Kotaemon is an open‑source, retrieval‑augmented generation (RAG) based tool that lets you build a chatbot capable of "chatting with your documents". As discussed in CVE-2026-86867, all versions up to v0.12.0 fail to verify conversation ownership when loading a conversation. In multi‑user mode, each conversation row includes a user field that identifies its owner. The four affected handlers, select_conv, delete_conv, rename_conv, and persist_chat_suggestions, query conversations using select(Conversation).where(Conversation.id == conversation_id)

No predicate is included to ensure Conversation.user == user_id. As a result, any authenticated user can operate on conversations they do not own.

Impacted operations include:
* select_conv – reads the full chat transcript, RAG retrieval history (verbatim excerpts from uploaded private documents), plot history, and suggestion data belonging to another user.
* delete_conv – permanently deletes a conversation.
* rename_conv – renames a conversation.
* persist_chat_suggestions – overwrites a chat suggestion list.