CVE-2026-16481: Server-Side Request Forgery (SSRF) and Credential Exfiltration in googleapis/mcp-toolbox cloud-healthcare-fhir-fetch-page Tool
A Server-Side Request Forgery (SSRF) and credential exfiltration vulnerability exists in the cloud-healthcare-fhir-fetch-page tool of googleapis/mcp-toolbox.
The tool takes an unvalidated pageURL parameter from the client and issues an HTTP GET request to it using an authenticated client. The underlying transport automatically attaches an Authorization: Bearer header to every outbound request regardless of the destination host. An attacker can supply an arbitrary external URL to the pageURL parameter (either directly via the tool execution payload or implicitly via data-driven pagination tracking loops), leading Toolbox into sending its OAuth/service-account access token to an attacker-controlled listener. Depending on the configuration, this leaks either the end-user's token or the broader service-account access token (ADC), potentially exposing Protected Health Information (PHI) and secondary Google Cloud Platform services.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Modify the cloud-healthcare-fhir-fetch-page tool to reject/validate the client-supplied pageURL parameter (and any data-driven pagination-derived pageURL) so outbound HTTP GET requests can only be made to an intended allowlisted host/path; do not permit arbitrary external URLs.
googleapis/mcp-toolbox cloud-healthcare-fhir-fetch-page tool pageURL parameter validation = validated allowlist - Compensating control
Ensure the HTTP transport/authenticated client used by cloud-healthcare-fhir-fetch-page does not automatically attach Authorization: Bearer access tokens to outbound requests when the destination host is not the trusted/expected host (prevent token attachment on arbitrary destinations to stop credential exfiltration via SSRF).
Event History
Frequently Asked Questions
What is the severity of CVE-2026-16481?
The severity of CVE-2026-16481 is rated as high at 8.4 on the CVSS scale.
How do I fix CVE-2026-16481?
To fix CVE-2026-16481, validate and sanitize the pageURL parameter to prevent untrusted inputs.
What type of vulnerability is CVE-2026-16481?
CVE-2026-16481 is identified as a Server-Side Request Forgery (SSRF) and credential exfiltration vulnerability.
Which software is affected by CVE-2026-16481?
The vulnerability CVE-2026-16481 affects the googleapis/mcp-toolbox, specifically the cloud-healthcare-fhir-fetch-page tool.
When was CVE-2026-16481 published?
CVE-2026-16481 was published on July 27, 2026.