CVE-2026-59973
mcp-from-openapi: Bypass of OpenAPI external $ref SSRF fix in latest FrontMCP and mcp-from-openapi
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High8.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N |
| NVDNVD · Deferred | 3.1 | High8.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N |
- EPSS (exploitation in 30 days)
- 0.39% · top 66% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.5.
Weakness
Affected products
- affected < 1.5.0
- affected < 2.5.0
- affected < 1.5.0
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- npm@frontmcp/adaptersGHSA-65h7-9wrw-629c (opens in a new tab)
- npmfrontmcpGHSA-65h7-9wrw-629c (opens in a new tab)
- npmmcp-from-openapiGHSA-65h7-9wrw-629c (opens in a new tab)
References (7)
- https://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c (opens in a new tab)x_refsource_CONFIRMexploit
- https://github.com/agentfront/frontmcp/pull/496 (opens in a new tab)x_refsource_MISC
- https://github.com/agentfront/mcp-from-openapi/pull/7 (opens in a new tab)x_refsource_MISC
- https://github.com/agentfront/frontmcp/commit/96a78eaa5c6c4bc51cced557d83d1a03344cb03d (opens in a new tab)x_refsource_MISC
- https://github.com/agentfront/mcp-from-openapi/commit/be3409cce6e97642696d4ee5a4e4e2712490b277 (opens in a new tab)x_refsource_MISC
- https://github.com/agentfront/frontmcp/releases/tag/v1.5.0 (opens in a new tab)x_refsource_MISC
- https://github.com/agentfront/mcp-from-openapi/releases/tag/v2.5.0 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-65h7-9wrw-629c (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-59973)Record last updated .