{"id":"CVE-2026-59973","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-59973","generatedAt":"2026-10-28T04:33:40.012Z","title":"This can expose internal administrative APIs, metadata-like services, and other private network endpoints.","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.","published":"2026-09-15T16:17:18.000Z","lastModified":"2026-09-30T17:51:56.000Z","status":"Deferred","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":8.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N"},"cwe":["CWE-918"],"affected":[],"epss":{"score":0.00393,"percentile":0.3329,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.39%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://github.com/agentfront/frontmcp/commit/96a78eaa5c6c4bc51cced557d83d1a03344cb03d","source":"security-advisories@github.com"},{"url":"https://github.com/agentfront/frontmcp/pull/496","source":"security-advisories@github.com"},{"url":"https://github.com/agentfront/frontmcp/releases/tag/v1.5.0","source":"security-advisories@github.com"},{"url":"https://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c","source":"security-advisories@github.com"},{"url":"https://github.com/agentfront/mcp-from-openapi/commit/be3409cce6e97642696d4ee5a4e4e2712490b277","source":"security-advisories@github.com"},{"url":"https://github.com/agentfront/mcp-from-openapi/pull/7","source":"security-advisories@github.com"},{"url":"https://github.com/agentfront/mcp-from-openapi/releases/tag/v2.5.0","source":"security-advisories@github.com"},{"url":"https://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-59973","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}