CVE-2026-39885 PUBLISHED

FrontMCP Affected by SSRF via $ref Dereferencing in Untrusted OpenAPI Specifications

Assigner: GitHub_M
Reserved: 07.04.2026 Published: 08.04.2026 Updated: 08.04.2026

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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS Score: 7.5

Product Status

Vendor agentfront
Product frontmcp
Versions
  • Version < 1.0.4 is affected
Vendor @frontmcp
Product adapters
Versions
  • Version < 1.0.4 is affected
Vendor @frontmcp
Product sdk
Versions
  • Version < 1.0.4 is affected
Vendor frontmcp
Product mcp-from-openapi
Versions
  • Version < 2.3.0 is affected

References

Problem Types

  • CWE-918: Server-Side Request Forgery (SSRF) CWE