CVE-2026-39885CWE-918

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

High · published April 8, 2026

CVSS v3.1
7.5
EPSS
0%
Percentile
35.5
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00423 · 35.5th percentile
Weakness
CWE-918 · Server-Side Request Forgery (SSRF)
Published
2026-04-08T20:34Z
EPSS history
Timeline
  • 08 APR 20:34Z
    FrontMCP Affected by SSRF via $ref Dereferencing in Untrusted OpenAPI Specifications
    cvelistv5