CVE-2026-61684

Deferred Deferred - Pending Action

Unauthenticated JWT Bypass in FastGPT Plugin

Publication date: 2026-07-15

Last updated on: 2026-07-15

Assigner: GitHub, Inc.

Description

FastGPT is a knowledge-based AI application platform. In 4.15.0-beta4, FastGPT plugin invoke reverse-call endpoints under /api/invoke/* authenticate only by verifying a JWT signed with INVOKE_TOKEN_SECRET, which defaults to the constant string token and was not set in official deployment templates. 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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-07-15

Last Modified

2026-07-15

Generated

2026-08-04

AI Q&A

2026-07-16

EPSS Evaluated

2026-08-03

NVD

CVE-2026-61684

EUVD

EUVD-2026-44676

Affected Vendors & Products

Vendor	Product	Version / Range
labring	fastgpt	4.15.0-beta4
labring	fastgpt	4.15.0-beta5
labring	fastgpt	4.15.0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-798	The product contains hard-coded credentials, such as a password or cryptographic key.

Attack-Flow Graph

Executive Summary

FastGPT versions 4.15.0 and earlier have a security flaw where plugin invoke endpoints under /api/invoke/* authenticate using a JWT signed with a default constant string 'token' for INVOKE_TOKEN_SECRET. This allows unauthenticated attackers to self-sign valid HS256 JWTs and bypass authentication on endpoints like /api/invoke/userInfo and /api/invoke/fileUpload.

Detection Guidance

Check if FastGPT is running version 4.15.0 or earlier. Inspect environment variables for INVOKE_TOKEN_SECRET being set to the default 'token' or missing entirely. Review logs for unauthorized access attempts to /api/invoke/userInfo or /api/invoke/fileUpload endpoints.

Impact Analysis

An attacker could access cross-tenant user PII such as usernames, emails, phone numbers, organization, and group memberships by exploiting the /api/invoke/userInfo endpoint. They could also write arbitrary content into chat files via the /api/invoke/fileUpload endpoint, potentially leading to data breaches or malware distribution.

Compliance Impact

This vulnerability could lead to unauthorized access to personally identifiable information (PII), violating GDPR's data protection principles and HIPAA's safeguards for protected health information. Non-compliance risks include legal penalties, reputational damage, and loss of trust.

Mitigation Strategies

Upgrade FastGPT to version 4.15.0-beta5 or later. Set a strong, random INVOKE_TOKEN_SECRET (minimum 32 characters) in environment variables. Ensure all deployment templates include this secret. Validate that JWT tokens are properly verified and user-controlled tmbId values are not trusted.

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