CVE-2026-39885 json
FrontMCP Affected by SSRF via $ref Dereferencing in Untrusted OpenAPI Specifications
published 2026-04-08 7 mo ago modified 2026-07-24 3 mo ago also GHSA-v6ph-xcq9-qxxj , EUVD-2026-20632
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 34%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- npm mcp-from-openapi 2.3.0
- npm @frontmcp/sdk 1.0.4
- npm @frontmcp/adapters 1.0.4
- agentfront @frontmcp/adapters 1.0.4
- agentfront @frontmcp/sdk 1.0.4
- agentfront frontmcp 1.0.4
- frontmcp mcp-from-openapi 2.3.0
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 7 mo ago
Exploit prediction
0.40% chance of exploitation in the next 30 days, higher than 34% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/agentfront/frontmcp/security/advisories/GHSA-v6ph-xcq9-qxxj referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
| GitHub | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| npm | mcp-from-openapi | <2.3.0 |
2.3.0 |
| npm | @frontmcp/sdk | <1.0.4 |
1.0.4 |
| npm | @frontmcp/adapters | <1.0.4 |
1.0.4 |
Affected products
- agentfront frontmcp
- @frontmcp adapters
- @frontmcp sdk
- frontmcp mcp-from-openapi
Classification
- Weakness
-
- CWE-918 Server-Side Request Forgery
References
-
github.com
/agentfront/frontmcp/security/advisories/GHSA-v6ph-xcq9-qxxj
exploit, web, vendor-advisory
-
github.com
/agentfront/frontmcp/releases/tag/v1.0.4
web, product
-
nvd.nist.gov
/vuln/detail/CVE-2026-39885
advisory
-
github.com
/agentfront/frontmcp
package
Sources
- CVE List CVE-2026-39885
- GitHub Advisory GHSA-v6ph-xcq9-qxxj
- NVD CVE-2026-39885
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.