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CVE-2026-42344— FastGPT: DNS rebinding TOCTOU bypass in isInternalAddress allows SSRF on all protected endpoints

Quick assessment

Affected
labring FastGPT
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

FastGPT是labring开源的一款基于大语言模型的开源知识库问答系统。 FastGPT 4.14.11及之前版本存在安全漏洞，该漏洞源于isInternalAddress函数存在DNS重新绑定漏洞，可能导致DNS记录在验证和获取之间发生变化。

CVSS 6.3 · Medium EPSS 0.15% · P5

Possible ATT&CK Techniques 1 AI

T1071 · Application Layer Protocol

Affected Version Matrix 1

VendorProduct Version RangeStatus
labring FastGPT <= 4.14.11 affected
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I. Basic Information for CVE-2026-42344

Vulnerability Information
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Vulnerability Title
FastGPT: DNS rebinding TOCTOU bypass in isInternalAddress allows SSRF on all protected endpoints
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
检查时间与使用时间(TOCTOU)的竞争条件
Source: CVE Program / CVE List V5
Vulnerability Title
FastGPT 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
FastGPT是labring开源的一款基于大语言模型的开源知识库问答系统。 FastGPT 4.14.11及之前版本存在安全漏洞，该漏洞源于isInternalAddress函数存在DNS重新绑定漏洞，可能导致DNS记录在验证和获取之间发生变化。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
labring FastGPT <= 4.14.11 -

II. Public POCs for CVE-2026-42344

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III. Intelligence Information for CVE-2026-42344

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Vendor Advisories for CVE-2026-42344 (1)

Same Patch Batch · labring · 2026-05-08 · 6 CVEs total

CVE-2026-42302 9.8 CRITICAL FastGPT: Unauthenticated Remote Code Execution (RCE) via code-server Misconfiguration in a
CVE-2026-42345 7.7 HIGH FastGPT: Cloud metadata endpoint SSRF protection bypass via port specification, IPv6 mappi
CVE-2026-44284 6.3 MEDIUM FastGPT: Stored MCP tool URL SSRF in FastGPT workflow execution
CVE-2026-42343 FastGPT: Uncontrolled Resource Consumption leading to Sandbox Exhaustion
CVE-2026-44286 FastGPT: SSRF Vulnerability in Laf Workflow Node via Missing Internal Address Validation

IV. Related Vulnerabilities

Same product: FastGPT
Same vendor: labring
Same weakness: CWE-367

V. Comments for CVE-2026-42344

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