GHSA-vv7q-7jx5-f767 · Severity: critical · Ecosystem: pip — FastMCP OpenAPI Provider has an SSRF & Path Traversal Vulnerability
FastMCP is a Pythonic way to build MCP servers and clients. Prior to version 3.2.0, the OpenAPIProvider in FastMCP exposes internal APIs to MCP clients by parsing OpenAPI specifications. The RequestDirector class is responsible for constructing HTTP requests to the backend service. A vulnerability exists in the _build_url() method. When an OpenAPI operation defines path parameters (e.g., /api/v1/users/{user_id}), the system directly substitutes parameter values into the URL template string without URL-encoding. Subsequently, urllib.parse.urljoin() resolves the final URL. Since urljoin() interprets ../ sequences as directory traversal, an attacker controlling a path parameter can perform path traversal attacks to escape the intended API prefix and access arbitrary backend endpoints. This results in authenticated SSRF, as requests are sent with the authorization headers configured in the MCP provider. This issue has been patched in version 3.2.0.
Conclusion & alert: CVE-2026-32871 is rated High Exploit Risk (63.4/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.08%). Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). Mandatory action: 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.
| EDB-ID | Source | Kind | Published | Link |
|---|---|---|---|---|
| — | nvd_ref | exploit_tag | Exploit-DB ↗ |
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 | 2026-04-21 | 0.15% | 0.08% | -0.07% |
| 2 | 2026-04-11 | 0.35% | 0.15% | -0.20% |
| 3 | 2026-04-08 | — | 0.35% | — |
Full EPSS history (4 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 10.0 | 4.0 | CRITICAL |
|
— | — | [email protected] |
| 10.0 | 3.1 | CRITICAL |
|
3.9 | 6.0 | [email protected] |
GHSA-vv7q-7jx5-f767 · Severity: critical · Ecosystem: pip — FastMCP OpenAPI Provider has an SSRF & Path Traversal Vulnerability
| vendor | priority | summary | link |
|---|---|---|---|
redhat
|
high | — | https://access.redhat.com/security/cve/CVE-2026-32871 |
| URL | Tags |
|---|---|
| https://github.com/PrefectHQ/fastmcp/commit/40bdfb6b1de0ce30609ee9ba5bb95ecd04a9fb71 | Patch |
| https://github.com/PrefectHQ/fastmcp/pull/3507 | Issue Tracking Patch |
| https://github.com/PrefectHQ/fastmcp/releases/tag/v3.2.0 | Product Release Notes |
| https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-vv7q-7jx5-f767 | Exploit Mitigation Vendor Advisory |