FastGPT versions before 4.15.0-beta5 contain an authorization bypass vulnerability (CWE-639) where two file handlers improperly authorize resources but then sign or read S3 objects using user-supplied keys without verifying that the key belongs to the caller's team. Because S3 object keys are global within the bucket and tenant identification is only part of the path, an attacker can supply keys belonging to other teams to access their files through the chat-file presign or dataset preview endpoints. This issue is resolved in version 4.15.0-beta5.

An attacker without privileges can access files belonging to other teams by supplying their S3 object keys, leading to unauthorized disclosure of sensitive data. The vulnerability affects confidentiality but does not impact integrity or availability. The CVSS 3.1 base score is 8.6 (high severity), reflecting network attack vector, low complexity, no privileges required, no user interaction, and high confidentiality impact with scope change.

The vendor has fixed this vulnerability in FastGPT version 4.15.0-beta5. Since this is a cloud service, the vendor manages remediation server-side. Users should verify with the vendor advisory that their service instance is updated to at least version 4.15.0-beta5 to ensure the vulnerability is mitigated.