High severity · published Apr 8, 2026
CVE-2026-39885
FrontMCP Affected by SSRF via $ref Dereferencing in Untrusted OpenAPI Specifications
7.5
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 34% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AD
adapters · @frontmcp
< 1.0.4 · source: vendor
FR
frontmcp · agentfront
< 1.0.4 · source: vendor, NVD
MC
mcp-from-openapi · frontmcp
< 2.3.0 · source: vendor, NVD
SD
sdk · @frontmcp
< 1.0.4 · source: vendor
FR
@frontmcp/adapters · Agentfront
before 1.0.4 · source: NVD
FR
@frontmcp/sdk · Agentfront
before 1.0.4 · source: NVD