Executive brief
FastGPT is an open-source platform used to build AI knowledge bases. A security flaw in how the system handles file requests allows an attacker to access private files belonging to other teams or users. This could lead to the unauthorized exposure of sensitive documents and data stored within the platform.
Technical details
A Broken Object Level Authorization (BOLA) vulnerability exists in FastGPT's file handling logic. The application fails to validate that a user-supplied S3 object key belongs to the requester's authorized team or tenant before generating a pre-signed URL or reading the file. Because S3 keys are global within a bucket and use predictable path segments for tenant IDs, an attacker can guess or obtain a key belonging to another team and access its contents via the `chat-file` presign or `dataset preview` endpoints. The fix, introduced in v4.15.0-beta5, implements strict binding between S3 object keys and the authorized resource context (app, dataset, or team) before any signing or read operations occur.
Affected products
- labring FastGPT < 4.15.0-beta5
Timeline
- 2026-06-12: patched: Fix committed to main branch
- 2026-06-24: advisory: Release v4.15.0-beta5 published
- 2026-07-07: disclosed: CVE-2026-55418 published