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Vulnerability · Published Apr 8, 2026 · Assigned by GitHub_M

CVE-2026-39885FrontMCP Affected by SSRF via $ref Dereferencing in Untrusted OpenAPI Specifications

High 7.5

In plain English

A high-severity server-side request forgery in frontmcp from agentfront. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.4%top 65.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official description

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 packages & fixed versions

EcosystemPackageFixed inAdvisory
npm@frontmcp/adapters1.0.4GHSA-v6ph-xcq9-qxxj
npm@frontmcp/sdk1.0.4GHSA-v6ph-xcq9-qxxj
npmmcp-from-openapi2.3.0GHSA-v6ph-xcq9-qxxj

Affected products (as reported)

VendorProductVersions
agentfront frontmcp < 1.0.4
@frontmcp adapters < 1.0.4
@frontmcp sdk < 1.0.4
frontmcp mcp-from-openapi < 2.3.0

Weakness: CWE-918 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References