{"id":"CVE-2026-11717","aliases":["GHSA-8fcc-w5hv-4gxv","GO-2026-5251"],"url":"https://o3.security/vulnerability/CVE-2026-11717","summary":"googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken)","details":"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.","published":"2026-06-18T11:50:23.665Z","modified":"2026-08-19T03:55:35.482200930Z","cvss":null,"epss":{"score":0.00176,"percentile":0.07344,"asOf":"2026-09-12"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/googleapis/mcp-toolbox","fixedVersion":"1.4.0"}],"fix":{"url":"https://github.com/googleapis/mcp-toolbox/pull/3341","label":"googleapis/mcp-toolbox#3341"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/11xxx/CVE-2026-11717.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-11717"},{"type":"FIX","url":"https://github.com/googleapis/mcp-toolbox/pull/3341"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-19T03:55:35.482200930Z"}}