LobeHub Vulnerable to Improper Authorization in Presigned Upload
Date: 2026-02
Affected: npm/@lobehub/chat
Attack vector: auth-bypass
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-23835
CWE: CWE-73

### Summary The file upload feature in `Knowledge Base > File Upload` does not validate the integrity of the upload request, allowing users to intercept and modify the request parameters. As a result, it is possible to create arbitrary files in abnormal or unintended paths. In addition, since `lobechat.com` relies on the size parameter from the request to calculate file usage, an attacker can manipulate this value to misrepresent the actual file size, such as uploading a `1 GB` file while reporting it as `10 MB`, or falsely declaring a `10 MB` file as a `1 GB` file. ### Details After entering the Knowledge Base, click the file upload option and upload any file. At this point, use a tool such as Burp Suite to intercept and inspect the request sent to `POST /trpc/lambda/file.createFile?batch=1` (the request packet is shown in the image below). By modifying the name and size fields in this request, it is possible to bypass the maximum upload size enforced by LobeChat’s monthly subscription plan and upload files beyond the intended service storage limits. <img width="670" height="413" alt="image" src="https://github.com/user-attachments/assets/c83cfb81-3bcc-4562-b052-5344ccf6356f" /> ### Impacts By manipulating the size value provided in the client upload request, it is possible to bypass the monthly upload quota enforced by the server and continuously upload files beyond the intended storage and traffic limits. This abuse can result in a discrepancy between actual resource con


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Architectural layers (MAESTRO):