CVE-2026-39885 FrontMCP Affected by SSRF via $ref Dereferencing in Untrusted OpenAPI Specifications
Attackers can trigger SSRF and local file reads by providing malicious OpenAPI specifications to the FrontMCP library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-39885?
CVE-2026-39885 is a high-severity server-side request forgery vulnerability in @frontmcp adapters, published on 8 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-918
Which versions are affected by CVE-2026-39885?
6 open source packages ship an affected version, including @frontmcp/adapters, @frontmcp/sdk and mcp-from-openapi. It affects 4 products.
| Package | Affected | Fixed in |
|---|---|---|
@frontmcp/adapters npm | All versions | 1.0.4 |
@frontmcp/adapters npm | All versions | 1.0.4 |
@frontmcp/sdk npm | All versions | 1.0.4 |
@frontmcp/sdk npm | All versions | 1.0.4 |
mcp-from-openapi npm | All versions | 2.3.0 |
mcp-from-openapi npm | All versions | 2.3.0 |
Products include Agentfront \@Frontmcp\/Adapters, Agentfront \@Frontmcp\/Sdk, Agentfront Frontmcp, Frontmcp Mcp-From-Openapi.
How do I fix CVE-2026-39885?
Upgrade @frontmcp/adapters to 1.0.4 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-39885 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39885 exists.
Sources
Also known as GHSA-v6ph-xcq9-qxxj.