CVE-2026-86867 in Kotaemon
Summary
by MITRE • 09/23/2026
Cinnamon's Kotaemon (all versions up to and including v0.12.0) multi-user chat interface contains multiple vulnerabilities due to incorrect authorization and improper access controls. There are four handler methods in `libs/ktem/ktem/pages/chat/control.py` that load a Conversation record by its ID without comparing the requester's `user_id` to the conversation's owner `Conversation.user`. This allows any authenticated user to perform the following actions: 1. Read other user's chat transcripts, RAG retrieval history, AI-generated plots, and chat suggestions. 2. Permanently delete another user's conversation. 3. Rename another user's conversation. 4. Overwrite another user's conversation's chat suggestion list.
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Analysis
by VulDB Data Team • 09/23/2026
The vulnerability identified in Cinnamon Kotaemon versions up to v0.12.0 represents a critical failure in server-side access control mechanisms, specifically within the multi-user chat interface component known as kotaemon. The core technical flaw resides in four handler methods located in the file libs/ktem/ktem/pages/chat/control.py. These endpoints are designed to manage conversation records by their unique identifiers but fail to implement proper authorization checks before executing operations on those records. Specifically, when a request is received containing a Conversation ID, the application retrieves and processes the corresponding database record without verifying that the user_id associated with the authenticated session matches the owner field stored within the Conversation object. This absence of an ownership validation step creates a direct path for insecure direct object references to be exploited by any authenticated actor interacting with the system.
From a technical perspective, this flaw allows for complete bypassing of intended data isolation boundaries between users in a multi-tenant environment. Because the application relies solely on the provided identifier rather than enforcing a relationship check against the current user's identity, an attacker can manipulate input parameters to target conversations belonging to other individuals. This is not merely a theoretical risk but a functional breach that impacts confidentiality, integrity, and availability simultaneously. The lack of object-level authorization means that internal identifiers are treated as public keys for data access rather than private references tied to specific entities, violating fundamental principles of secure software design regarding resource ownership verification.
The operational impact of this vulnerability is severe due to the breadth of actions enabled by these flawed handlers. First, an attacker can read sensitive chat transcripts from other users, which may contain proprietary information, personal details, or confidential business logic discussed within the application. Additionally, the attacker gains access to Retrieval-Augmented Generation retrieval history and AI-generated plots associated with those conversations, exposing underlying data sources and analytical outputs that were not intended for public view. The ability to read chat suggestions further compromises user privacy by revealing inferred intents or contextual metadata generated by the system's artificial intelligence components.
Beyond confidentiality breaches, the vulnerability permits significant integrity violations through unauthorized modification of other users' data. An attacker can permanently delete another user’s conversation history, resulting in irreversible loss of information and disrupting workflow continuity for victims. Furthermore, the ability to rename conversations allows an attacker to mislead or confuse users by altering metadata that serves as primary navigation aids within the interface. The capability to overwrite a user's chat suggestion list introduces additional integrity risks, potentially injecting misleading prompts or removing helpful contextual hints provided by the AI assistant, thereby degrading the quality of service and manipulating user interactions with the platform.
This vulnerability aligns directly with CWE-284, which describes Improper Access Control, specifically reflecting scenarios where access control decisions are not enforced properly on critical resources. In terms of offensive security frameworks, this behavior maps to ATT&CK technique T1078, Valid Accounts, as exploitation requires initial authentication but then leverages those credentials to escalate privileges over data ownership boundaries. It also relates to CWE-639, Authorization Bypass Through User-Controlled Key, since the primary vector for abuse is the manipulation of the conversation identifier without validating its association with the requesting user's account context.
Mitigation strategies must prioritize immediate implementation of robust authorization checks within the affected handler methods in libs/ktem/ktem/pages/chat/control.py. Developers should enforce a strict verification step that compares the authenticated session’s user_id against the owner field of the targeted Conversation record before allowing any read, write, or delete operations to proceed. If this comparison fails, the system must return an appropriate error code indicating insufficient permissions rather than executing the requested action. Additionally, implementing principle of least privilege ensures that users only have access to resources explicitly assigned to them. Regular security audits and static analysis tools configured to detect missing authorization checks in object-oriented handlers can help prevent similar flaws from being introduced during future development cycles.