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

Exp

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.

Published: 2026-04-08 Last update: 2026-04-15 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-39885 is rated Exploit Available (51.7/100): CVSS High severity, with low exploitation likelihood (EPSS 0.06%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-39885

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-39885

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-20 0.03% 0.06% +0.03%
2 2026-04-09 — 0.03% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-39885

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2026-39885

GitHub Security Advisory for CVE-2026-39885

GHSA-v6ph-xcq9-qxxj · Severity: high · Ecosystem: npm — mcp-from-openapi is Vulnerable to SSRF via $ref Dereferencing in Untrusted OpenAPI Specifications

Affected software / configurations for CVE-2026-39885

Vendor Product Version Raw CPE
agentfront \@frontmcp\/adapters < 1.0.4 cpe:2.3:a:agentfront:\@frontmcp\/adapters:*:*:*:*:*:node.js:*:*
agentfront \@frontmcp\/sdk < 1.0.4 cpe:2.3:a:agentfront:\@frontmcp\/sdk:*:*:*:*:*:node.js:*:*
agentfront frontmcp < 1.0.4 cpe:2.3:a:agentfront:frontmcp:*:*:*:*:*:node.js:*:*
frontmcp mcp-from-openapi < 2.3.0 cpe:2.3:a:frontmcp:mcp-from-openapi:*:*:*:*:*:node.js:*:*

References for CVE-2026-39885

cvelogic Threat Intelligence