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CVE-2026-59973— mcp-from-openapi: Bypass of OpenAPI external $ref SSRF fix in latest FrontMCP and mcp-from-openapi

Quick assessment

Affected
agentfront frontmcp
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.

AgentFront FrontMCP是AgentFront组织开源的一个基于TypeScript的MCP服务器开发框架。 AgentFront FrontMCP存在服务端请求伪造漏洞，该漏洞源于文件 libs/adapters/src/openapi/openapi.adapter.ts 中的 loadOpenAPISpec() 函数将不受信任的 OpenAPI url、spec 输入及 loadOptions.refResolution 转发给 OpenAPIToolGenerator.fromURL

CVSS 8.5 · High EPSS 0.39% · P31

Possible ATT&CK Techniques 1 AI

T1011.004

Affected Version Matrix 3

VendorProduct Version RangeStatus
@frontmcp adapters < 1.5.0 affected
agentfront frontmcp < 1.5.0 affected
agentfront mcp-from-openapi < 2.5.0 affected
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I. Basic Information for CVE-2026-59973

Vulnerability Information
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Vulnerability Title
mcp-from-openapi: Bypass of OpenAPI external $ref SSRF fix in latest FrontMCP and mcp-from-openapi
Source: CVE Program / CVE List V5
Vulnerability Description
FrontMCP is a TypeScript-first framework for the Model Context Protocol (MCP). From mcp-from-openapi 2.3.0 until 2.5.0 and from frontmcp and @frontmcp/adapters 1.2.1 until 1.5.0, libs/adapters/src/openapi/openapi.adapter.ts loadOpenAPISpec() forwards untrusted OpenAPI url and spec inputs and loadOptions.refResolution to OpenAPIToolGenerator.fromURL() and OpenAPIToolGenerator.fromJSON(). The external $ref guard checks parsed hostname strings without resolving addresses, pinning validated addresses, revalidating redirect targets, or normalizing IPv4-mapped IPv6. An authenticated user who can import or configure an OpenAPI specification in a hosted or multi-user deployment can use DNS-to-loopback resolution, redirect-to-loopback behavior, or IPv4-mapped IPv6 loopback forms to cause backend-origin requests to internal services. This can expose internal administrative APIs, metadata-like services, and other private network endpoints. The practical impact is lower when only a trusted local administrator can configure OpenAPI specs, and disabling external reference protocols prevents the external $ref request. This issue is fixed in mcp-from-openapi 2.5.0 and frontmcp and @frontmcp/adapters 1.5.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
AgentFront FrontMCP 服务端请求伪造漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
AgentFront FrontMCP是AgentFront组织开源的一个基于TypeScript的MCP服务器开发框架。 AgentFront FrontMCP存在服务端请求伪造漏洞，该漏洞源于文件 libs/adapters/src/openapi/openapi.adapter.ts 中的 loadOpenAPISpec() 函数将不受信任的 OpenAPI url、spec 输入及 loadOptions.refResolution 转发给 OpenAPIToolGenerator.fromURL
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
agentfront frontmcp < 1.5.0 -
agentfront mcp-from-openapi < 2.5.0 -
@frontmcp adapters < 1.5.0 -

II. Public POCs for CVE-2026-59973

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III. Intelligence Information for CVE-2026-59973

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Patches & Fixes for CVE-2026-59973 (2)

Vendor Advisories for CVE-2026-59973 (1)

Vendor Pages for CVE-2026-59973 (2)

IV. Related Vulnerabilities

Same product: frontmcp
Same vendor: agentfront
Same weakness: CWE-918

V. Comments for CVE-2026-59973

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