CVE-2026-23835: LobeHub Vulnerable to Improper Authorization in Presigned Upload

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.