{"id":"GHSA-8fcc-w5hv-4gxv","revision":"f8adaa472b8442d59ba82a4d9473d1cf","records":[{"revision":"f8adaa472b8442d59ba82a4d9473d1cf","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GHSA-8fcc-w5hv-4gxv","aliases":["CVE-2026-11717","GO-2026-5251"],"title":"googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken)","description":"An authentication bypass vulnerability exists in the generic opaque token validation path (validateOpaqueToken) of googleapis/mcp-toolbox.\n\nWhen verifying an unparsed opaque token via an OAuth 2.0 introspection endpoint (RFC 7662), the toolbox decodes the response into an introspectResp struct where the Active field is declared as a pointer to a boolean (*bool). The code only explicitly rejects a token if the response contains a populated active field set to false (if introspectResp.Active != nil && !*introspectResp.Active). If an introspection endpoint responds with a payload that completely omits the mandatory active key, the internal variable remains nil, causing the conditional check to short-circuit. As a result, Toolbox accepts authorization tokens missing the \"active\" field, granting access to protected tools and underlying data sources.","state":0,"publishedAt":"2026-06-18T15:32:01+00:00","modifiedAt":"2026-06-25T19:56:37.7815438+00:00","affected":[{"ecosystem":"Go","name":"github.com/googleapis/mcp-toolbox","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"1.4.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V4","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"CRITICAL"}],"references":["https://nvd.nist.gov/vuln/detail/CVE-2026-11717","https://github.com/googleapis/mcp-toolbox/pull/3341","https://github.com/googleapis/mcp-toolbox"],"sourceUrl":"https://github.com/advisories/GHSA-8fcc-w5hv-4gxv","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-8fcc-w5hv-4gxv","identifiers":["GHSA-8fcc-w5hv-4gxv","CVE-2026-11717","GO-2026-5251"]},"retained":false,"historicalAffected":[]}],"coverage":[]}