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PatchSiren cyber security CVE debrief

CVE-2026-16481 Google CVE debrief

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.

Vendor
Google
Product
MCP Toolbox for Databases (googleapis/mcp-toolbox)
CVSS
MEDIUM 6
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-27
Original CVE updated
2026-09-28
Advisory published
2026-07-27
Advisory updated
2026-09-28

Who should care

Defenders responsible for configuring and securing googleapis/mcp-toolbox, especially those handling service accounts and OAuth tokens, should assess exposure and prioritize verification.

Why it matters

CVE-2026-16481 is a medium-severity vulnerability in googleapis/mcp-toolbox that allows SSRF and credential exfiltration. Defenders should prioritize verifying exposure, assessing configuration, and implementing compensating controls to limit the scope of OAuth/service-account access tokens.

  • Credential exfiltration may expose Protected Health Information (PHI)
  • Potential impact on secondary Google Cloud Platform services
  • Requires verification of affected versions and configurations
  • Defenders should monitor for suspicious activity related to the affected tool

Technical summary

The cloud-healthcare-fhir-fetch-page tool of googleapis/mcp-toolbox is vulnerable to Server-Side Request Forgery (SSRF) and credential exfiltration. An attacker can supply an arbitrary external URL to the pageURL parameter, leading Toolbox into sending its OAuth/service-account access token to an attacker-controlled listener. This vulnerability allows an attacker to exfiltrate credentials, potentially exposing Protected Health Information (PHI) and secondary Google Cloud Platform services. Defenders should prioritize verifying exposure and assessing configuration, especially for service accounts and OAuth tokens, and implement compensating controls to limit the scope of OAuth/service-account access tokens.

Defensive priority

Defenders should prioritize verifying exposure and assessing configuration, especially for service accounts and OAuth tokens.

Recommended defensive actions

  • Verify exposure by checking the configuration of the cloud-healthcare-fhir-fetch-page tool
  • Assess the impact of potential credential exfiltration on secondary Google Cloud Platform services
  • Implement compensating controls to limit the scope of OAuth/service-account access tokens
  • Monitor for suspicious activity related to the affected tool
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The vulnerability allows an attacker to exfiltrate credentials, potentially exposing PHI and secondary Google Cloud Platform services. The CVE record and NVD entry provide details on the vulnerability and affected versions.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-16481 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-16481

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-16481 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-16481

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.