CVE-2026-32871
Description
A flaw was found in FastMCP. An authenticated attacker can exploit a path traversal vulnerability in the _build_url() method of the RequestDirector class. By manipulating path parameters in an OpenAPI operation, an attacker can use directory traversal sequences (../) to bypass the intended API prefix. This allows the attacker to access arbitrary backend endpoints, leading to authenticated Server-Side Request Forgery (SSRF). Server-Side Request Forgery (SSRF) enables an attacker to compel the server-side application to send HTTP requests to an arbitrary domain.
Statement
This is an Important severity flaw affecting FastMCP, which is utilized in Red Hat OpenShift AI, Red Hat Satellite, Hosted OpenShift Clusters, and Ansible Services. An authenticated attacker can exploit a path traversal vulnerability in FastMCP's OpenAPI path parameter handling to achieve Server-Side Request Forgery (SSRF), allowing access to arbitrary backend endpoints. As a result of a successful exploitation of this vulnerability the attacker may be able to access private endpoints, exfiltrate data, achieving privilege escalation or by-pass security controls within the affected component.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.5 | 10 | 8.5 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | High |
| Privileges Required | Low | None | Low |
| User Interaction | None | None | None |
| Scope | Changed | Changed | Changed |
| Confidentiality | High | High | High |
| Integrity Impact | High | High | High |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Integrity
Technical Impact: Execute Unauthorized Code or Commands
Access Control
Technical Impact: Bypass Protection Mechanism
By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
Frequently Asked Questions
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