GHSA-8Q49-2H5H-434X: GHSA-8Q49-2H5H-434X: Server-Side Request Forgery in FrontMCP OpenAPI Spec Poller

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GHSA-8Q49-2H5H-434X: Server-Side Request Forgery in FrontMCP OpenAPI Spec Poller

Vulnerability ID: GHSA-8Q49-2H5H-434X
CVSS Score: 8.6
Published: 2026-07-24

A Server-Side Request Forgery (SSRF) vulnerability in FrontMCP allows unauthenticated remote attackers to query internal network services by exploiting the un-guarded background OpenAPI specification polling mechanism.

TL;DR

The FrontMCP background spec poller used an un-guarded global fetch() call, bypassing initial SSRF protections and allowing attackers to query internal interfaces via DNS rebinding or HTTP redirects.

⚠️ Exploit Status: POC

Technical Details

CWE ID: CWE-918
Attack Vector: Network (AV:N)
CVSS Score: 8.6 (High)
Exploit Status: Proof of Concept
KEV Status: Not Listed
Vulnerability Impact: Server-Side Request Forgery

Affected Systems

FrontMCP
@frontmcp/sdk
@frontmcp/adapters
@frontmcp/sdk: < 1.5.6 (Fixed in: 1.5.6)
@frontmcp/adapters: < 1.5.6 (Fixed in: 1.5.6)

Code Analysis

Commit: 077201e

SECURITY (GHSA-65h7-9wrw-629c): guard the polled spec URL like fromURL() instead of raw fetch.

Mitigation Strategies

Upgrade FrontMCP dependency suites to v1.5.6 or higher.
Retain default blocked networks behavior (avoid setting allowInternalIPs to true in production configurations).
Restrict network communications of the runner runtime to allowlisted external domains.

Remediation Steps:

Execute dependency updates: 'npm install @frontmcp/sdk@1.5.6 @frontmcp/adapters@1.5.6'.
Review application initializations to guarantee custom allowedHosts settings cover authorized specifications.
Redeploy services and verify outgoing communication alerts to identify illegal internal lookups.

References

Read the full report for GHSA-8Q49-2H5H-434X on our website for more details including interactive diagrams and full exploit analysis.

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