FrontMCP — Ssrf (CVE-2026-39885)
Date: 2026-04
Affected: agentfront/\@frontmcp\/adapters, agentfront/\@frontmcp\/sdk, agentfront/frontmcp, frontmcp/mcp-from-openapi
Attack vector: ssrf
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2026-39885
CWE: CWE-918
CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N)

FrontMCP is a TypeScript-first framework for the Model Context Protocol (MCP). Prior to 2.3.0, the mcp-from-openapi library uses @apidevtools/json-schema-ref-parser to dereference $ref pointers in OpenAPI specifications without configuring any URL restrictions or custom resolvers. A malicious OpenAPI specification containing $ref values pointing to internal network addresses, cloud metadata endpoints, or local files will cause the library to fetch those resources during the initialize() call. This enables Server-Side Request Forgery (SSRF) and local file read attacks when processing untrusted OpenAPI specifications. This vulnerability is fixed in 2.3.0.


Mitigations:

Architectural layers (MAESTRO):