CVE-2026-39885

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

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.

Affected

agentfront · @frontmcp · frontmcp · adapters · sdk · mcp-from-openapi

CVSS v3.1 GITHUB

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

EPSS

0.42% chance of exploitation in the next 30 days, 35th percentile

Published

2026-04-08

Updated

2026-04-09

Proof-of-concept exploits (1)

• advisories/GHSA-v6ph-xcq9-qxxj

Security advisories

• agentfront/frontmcp/security/advisories/GHSA-v6ph-xcq9-qxxj
• agentfront/frontmcp/releases/tag/v1.0.4

References

• CVE Record
• NVD entry