---
id: CVE-2026-19202
title: >-
  A caching flaw in the toolbox-core package of the mcp-toolbox-sdk-python SDK
  causes the same Google ID token to be cached and reused across different
  audiences
summary: >-
  A caching flaw in the toolbox-core package of the mcp-toolbox-sdk-python SDK
  causes the same Google ID token to be cached and reused across different
  audiences. If an application uses the SDK to authenticate to two or more
  different audi…
severity: critical
cvss: 9.1
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N'
cwe:
  - CWE-524
vendor: Google
product: mcp-toolbox-sdk-python
affected:
  - mcp-toolbox-sdk-python <= 1.1.0
published: '2026-09-22'
updated: '2026-09-23'
sourceUpdated: '2026-09-23T19:42:48.540'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-19202'
references:
  - url: 'https://github.com/googleapis/mcp-toolbox-sdk-python/pull/675'
    label: cve-coordination@google.com
tags:
  - nvd
  - cve.org
epss: 0.0025
epssPercentile: 0.14506
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-09-23T15:01:44.032567Z'
cvssSource: cna
ingestedAt: '2026-09-22T22:12:45.117Z'
---

## Overview

A caching flaw in the toolbox-core package of the mcp-toolbox-sdk-python SDK causes the same Google ID token to be cached and reused across different audiences. If an application uses the SDK to authenticate to two or more different audiences within the same process, the module-level token cache fails to key its cached tokens by the requested audience. Consequently, a valid, unexpired token minted for a sensitive service (Service A) can be retrieved from the cache and sent to a secondary service (Service B). An attacker who operates, compromises, or monitors traffic to Service B can capture this token and replay it to impersonate the victim application against Service A.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.