CVE-2026-55418 labring CVE debrief

Who should care

Users of FastGPT versions prior to v4.15.0-beta5 should apply the patch to prevent unauthorized access to S3 object contents. Affected operators, platforms, vulnerability-management, and security teams should review the official advisory and CVE record to validate affected scope, severity, and vendor guidance. They should also plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.

Technical summary

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. This allows an attacker to supply another team's key and obtain its file contents through the chat-file presign endpoint or dataset preview endpoint. The issue is fixed in version v4.15.0-beta5. The vulnerability has a CVSS score of 8.6 and is classified as HIGH severity.

Defensive priority

High priority due to the potential for unauthorized data access.

Recommended defensive actions

• Apply the patch to upgrade to v4.15.0-beta5 or later
• Review and restrict access to S3 object keys
• Monitor for suspicious activity on chat-file presign and dataset preview endpoints
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and NVD entry provide limited information about the vulnerability. Further investigation is needed to fully understand the impact and affected scope. The vulnerability affects FastGPT versions prior to v4.15.0-beta5. The issue allows an attacker to supply another team's key and obtain its file contents through the chat-file presign endpoint or dataset preview endpoint. Evidence is limited to CVE and NVD entries. Defenders should verify affected product deployments, review official advisories, and plan vendor-supported updates or mitigations.

Official resources