CVE-2026-42344
Received Received - Intake
DNS Rebinding Vulnerability in FastGPT AI Agent Platform

Publication date: 2026-05-08

Last updated on: 2026-05-11

Assigner: GitHub, Inc.

Description
FastGPT is an AI Agent building platform. In versions 4.14.11 and prior, FastGPT's isInternalAddress() function in packages/service/common/system/utils.ts is vulnerable to DNS rebinding (TOCTOU — Time-of-Check to Time-of-Use). The function resolves the hostname via dns.resolve4()/dns.resolve6() and checks resolved IPs against private ranges, but the actual HTTP request happens in a separate call with a new DNS resolution, allowing the DNS record to change between validation and fetch. At time of publication, there are no publicly available patches.
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Meta Information
Published
2026-05-08
Last Modified
2026-05-11
Generated
2026-06-19
AI Q&A
2026-05-09
EPSS Evaluated
2026-06-18
NVD
CVE-2026-42344
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
fastgpt fastgpt to 4.14.11 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-367 The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
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Executive Summary

This vulnerability exists in FastGPT versions 4.14.11 and earlier, specifically in the isInternalAddress() function. The function attempts to verify if a hostname resolves to a private IP address by resolving the hostname's IP addresses and checking them against private IP ranges. However, the actual HTTP request is made after a separate DNS resolution, allowing the DNS record to change between the initial check and the request (a Time-of-Check to Time-of-Use or TOCTOU issue). This enables DNS rebinding attacks, where an attacker can manipulate DNS responses to bypass security checks.

Impact Analysis

The vulnerability can allow an attacker to bypass internal address checks by exploiting the DNS rebinding flaw. This could lead to unauthorized access to internal or private network resources that should be protected, potentially exposing sensitive data or services. Since the CVSS score indicates a moderate severity with high confidentiality impact, the main risk is unauthorized disclosure of sensitive information.

Mitigation Strategies

At the time of publication, there are no publicly available patches for this vulnerability.

Given the nature of the DNS rebinding vulnerability in FastGPT versions 4.14.11 and prior, immediate mitigation steps could include restricting DNS responses to trusted IP ranges, implementing network-level DNS filtering, or isolating vulnerable services until a patch is available.

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