Vulnerability · Published Sep 22, 2026 · Assigned by Google
CVE-2026-19202Token Cache Reuse in mcp-toolbox-sdk-python
Critical 9.1
In plain English
A critical-severity security flaw in mcp-toolbox-sdk-python from Google. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 14% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| mcp-toolbox-sdk-python | 0 – through 1.1.0 |
Weakness: CWE-524 · Vector: 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