{"cve":"CVE-2026-59973","nvd":{"published":"2026-09-15T16:17:18.327","modified":"2026-09-30T17:51:56.193","status":"Deferred","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N","score":8.5},"cwes":["CWE-918"],"references":["https://github.com/agentfront/frontmcp/commit/96a78eaa5c6c4bc51cced557d83d1a03344cb03d","https://github.com/agentfront/frontmcp/pull/496","https://github.com/agentfront/frontmcp/releases/tag/v1.5.0","https://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c","https://github.com/agentfront/mcp-from-openapi/commit/be3409cce6e97642696d4ee5a4e4e2712490b277"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:53:43.293028046+00:00"},"epss":{"cve":"CVE-2026-59973","score":0.00393,"percentile":0.33184,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-65h7-9wrw-629c","url":"https://osv.dev/vulnerability/GHSA-65h7-9wrw-629c","summary":"FrontMCP and mcp-from-openapi have bypass of OpenAPI external $ref SSRF fix","modified":"2026-09-11T22:15:04.009061077Z","packages":[{"ecosystem":"npm","name":"mcp-from-openapi","purl":"pkg:npm/mcp-from-openapi","ranges":[">=2.3.0 <2.5.0"],"fixed":["2.5.0"]},{"ecosystem":"npm","name":"@frontmcp/adapters","purl":"pkg:npm/%40frontmcp/adapters","ranges":[">=1.2.1 <1.5.0"],"fixed":["1.5.0"]},{"ecosystem":"npm","name":"frontmcp","purl":"pkg:npm/frontmcp","ranges":[">=1.2.1 <1.5.0"],"fixed":["1.5.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}