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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-59973
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-15 16:17:18 UTC
Updated2026-09-16 17:17:28 UTC
DescriptionFrontMCP 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.

Risk And Classification

Primary CVSS: v3.1 8.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N

EPSS: 0.003760000 probability, percentile 0.312730000 (date 2026-09-16)

Problem Types: CWE-918 | CWE-918 CWE-918: Server-Side Request Forgery (SSRF)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.5HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
3.1CNADECLARED8.5HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Agentfront Frontmcp affected < 1.5.0 Not specified
CNA Agentfront Mcp-from-openapi affected < 2.5.0 Not specified
CNA @frontmcp Adapters affected < 1.5.0 Not specified

References

ReferenceSourceLinkTags
github.com/agentfront/mcp-from-openapi/releases/tag/v2.5.0 [email protected] github.com
github.com/agentfront/frontmcp/releases/tag/v1.5.0 [email protected] github.com
github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/agentfront/mcp-from-openapi/commit/be3409cce6e97642696d4ee5a4... [email protected] github.com
github.com/agentfront/frontmcp/commit/96a78eaa5c6c4bc51cced557d83d1a0334... [email protected] github.com
github.com/agentfront/frontmcp/pull/496 [email protected] github.com
github.com/agentfront/mcp-from-openapi/pull/7 [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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