FrontMCP and mcp-from-openapi have bypass of OpenAPI external $ref SSRF fix — GHSA-65H7-9WRW-629C

Summary

## Summary The published fix for GHSA-v6ph-xcq9-qxxj / CVE-2026-39885 added a direct hostname denylist for OpenAPI external `$ref` dereferencing, but the latest patched dependency `mcp-from-openapi` 2.3.0 still makes backend-origin requests to loopback when the target is reached through hostname resolution, redirects, or IPv4-mapped IPv6 syntax. FrontMCP latest release v1.2.1 and current main still call…

Timeline

Published by source

2026-09-11

Risk context

• Reported severity or threat level: high.
• Reported CVSS score: 8.5 out of 10.
• Review exposure for the affected product or family: npm: mcp-from-openapi | npm: @frontmcp/adapters | npm: frontmcp.

Product

npm: mcp-from-openapi | npm: @frontmcp/adapters | npm: frontmcp

What to do

General, cautious steps (verify details in the official source):

• Prioritize patching or mitigation immediately (treat as actively risky).
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-65H7-9WRW-629C

Source

GitHub

Vendor

GitHub

Published by source

2026-09-11

Last source activity

2026-09-11

Additional identifiers

CVE-2026-59973

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.