CVE-2026-70488 in Open WebUI
Summary
by MITRE • 08/05/2026
Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.6 until 0.11.0, the sync cleanup endpoint authorized write access to the knowledge base in the URL but then acted on directory and file ids supplied in the request body without checking that those objects belonged to that knowledge base. A user with write access to one knowledge base could delete directories and remove file embeddings from another knowledge base, causing documents to drop out of retrieval results and breaking chat-with-file for targeted documents without disclosing contents. This issue is fixed in 0.11.0.
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Analysis
by VulDB Data Team • 08/05/2026
The vulnerability described represents a critical authorization bypass flaw in Open WebUI version range 0.9.6 through 0.11.0, where the sync cleanup endpoint suffers from improper access control validation. This weakness stems from a fundamental design flaw in the permission model that allows arbitrary manipulation of knowledge base resources across different user contexts. The vulnerability specifically affects the endpoint responsible for cleaning up synchronization data within the platform's knowledge management system.
The technical implementation of this flaw occurs at the application logic level where the system accepts a knowledge base identifier from the URL path but subsequently processes directory and file identifiers from the request body without performing proper ownership verification. This creates a scenario where a malicious actor with write privileges to one knowledge base can craft requests that target resources belonging to different knowledge bases through the cleanup endpoint. The flaw essentially allows privilege escalation through resource manipulation, enabling unauthorized deletion of directory structures and removal of file embeddings.
The operational impact of this vulnerability extends beyond simple data loss, as it fundamentally compromises the integrity of the retrieval system within the AI platform. When files are removed from one knowledge base through manipulation of another's cleanup endpoint, documents cease to appear in search results and break chat-with-file functionality for those specific resources. This degradation affects the core utility of the platform while maintaining confidentiality since content is not disclosed but rather made unavailable through deletion. The vulnerability affects all users who have write access to any knowledge base within the system.
Security implications align with CWE-285, which addresses improper authorization in software systems, and can be mapped to ATT&CK technique T1499.004 for data destruction through deletion of files or directories. The vulnerability demonstrates a classic case of insufficient input validation combined with inadequate access control mechanisms that allow cross-contamination of resources within the same application instance. Organizations relying on this platform face potential service disruption and data integrity issues that could impact productivity and user trust in the AI system's reliability.
Mitigation strategies should focus on implementing robust access control checks at the endpoint level, ensuring that all resource identifiers in request bodies are validated against the knowledge base context provided in the URL path. The fix implemented in version 0.11.0 demonstrates proper authorization enforcement through validation of resource ownership before processing cleanup operations. Additional recommendations include implementing comprehensive logging of cleanup operations, establishing resource isolation boundaries, and conducting regular security audits of API endpoint access controls to prevent similar authorization bypass vulnerabilities from emerging in future releases.