---
cve: "CVE-2026-59973"
severity: "HIGH"
cvss: 8.5
epss: "0.4%"
vendor: "agentfront"
kev: false
exploited: false
published: "2026-09-15 15:13:40"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-22T21:52:17+02:00"
---

# CVE-2026-59973

> 8.5 HIGH · 🧪 PoC

## Beschreibung

FrontMCP is a TypeScript-first framework for the Model Context Protocol (MCP). From mcp-from-openapi 2.3.0 until 2.5.0 and from frontmcp and @frontmcp/adapters 1.2.1 until 1.5.0, libs/adapters/src/openapi/openapi.adapter.ts loadOpenAPISpec() forwards untrusted OpenAPI url and spec inputs and loadOptions.refResolution to OpenAPIToolGenerator.fromURL() and OpenAPIToolGenerator.fromJSON(). The external $ref guard checks parsed hostname strings without resolving addresses, pinning validated addresses, revalidating redirect targets, or normalizing IPv4-mapped IPv6. An authenticated user who can import or configure an OpenAPI specification in a hosted or multi-user deployment can use DNS-to-loopback resolution, redirect-to-loopback behavior, or IPv4-mapped IPv6 loopback forms to cause backend-origin requests to internal services. This can expose internal administrative APIs, metadata-like services, and other private network endpoints. The practical impact is lower when only a trusted local administrator can configure OpenAPI specs, and disabling external reference protocols prevents the external $ref request. This issue is fixed in mcp-from-openapi 2.5.0 and frontmcp and @frontmcp/adapters 1.5.0.

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |
| UI Interaktion | Keine | bad |
| S Scope | Verändert | bad |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Gering | warn |
| A Verfügbarkeit | Keine | good |

## Patch verfügbar (OSV)

- 96a78eaa5c6c4bc51cced557d83d1a03344cb03d (Commit)
- c1740dc4fd6a10e42f771b2c7715d2e091ec5d0e (Commit)

## Referenzen

- <https://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c>
- <https://github.com/agentfront/frontmcp/pull/496>
- <https://github.com/agentfront/mcp-from-openapi/pull/7>
- <https://github.com/agentfront/frontmcp/commit/96a78eaa5c6c4bc51cced557d83d1a03344cb03d>
- <https://github.com/agentfront/mcp-from-openapi/commit/be3409cce6e97642696d4ee5a4e4e2712490b277>
- <https://github.com/agentfront/frontmcp/releases/tag/v1.5.0>
- <https://github.com/agentfront/mcp-from-openapi/releases/tag/v2.5.0>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-59973) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_