CVE-2026-61684 labring CVE debrief

Who should care

Defenders responsible for FastGPT deployments, particularly those using version 4.15.0-beta4, should assess exposure and prioritize upgrading to version 4.15.0-beta5 or later. They should review official deployment templates for INVOKE_TOKEN_SECRET configuration and monitor for unauthorized access. Affected operators, platforms, vulnerability-management, and security teams should be informed about the potential impacts and necessary actions.

Why it matters

CVE-2026-61684 allows unauthenticated attackers to disclose user PII or write attacker-controlled content in FastGPT version 4.15.0-beta4. Defenders should verify and upgrade to version 4.15.0-beta5 or later, review official deployment templates for INVOKE_TOKEN_SECRET configuration, and monitor for unauthorized access.

• Disclosure of cross-tenant user PII
• Writing of attacker-controlled content into chat files
• Potential unauthorized access to sensitive information
• Verification of INVOKE_TOKEN_SECRET configuration and upgrade to fixed version

Technical summary

In FastGPT version 4.15.0-beta4, the plugin invoke reverse-call endpoints under /api/invoke/* authenticate only by verifying a JWT signed with INVOKE_TOKEN_SECRET, which defaults to a constant string token. An unauthenticated attacker can self-sign an HS256 JWT and reach /api/invoke/userInfo to disclose cross-tenant user PII by attacker-supplied tmbId values, or /api/invoke/fileUpload to write attacker-controlled content into chat files. This issue is fixed in version 4.15.0-beta5.

Defensive priority

Defenders should prioritize verifying and upgrading to version 4.15.0-beta5 or later, and review official deployment templates for INVOKE_TOKEN_SECRET configuration.

Recommended defensive actions

• Verify and upgrade to FastGPT version 4.15.0-beta5 or later
• Review official deployment templates for INVOKE_TOKEN_SECRET configuration
• Monitor for unauthorized access to /api/invoke/* endpoints
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The CVE record and NVD entry provide details on the vulnerability in FastGPT version 4.15.0-beta4. Official source references include commits, pull requests, and security advisories related to the fix in version 4.15.0-beta5.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.