{"id":"CVE-2026-11717","title":"googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken)","summary":"googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken)","severity":"critical","cwe":["CWE-287"],"vendor":"googleapis","product":"github.com/googleapis/mcp-toolbox","ecosystem":"go","affected":["github.com/googleapis/mcp-toolbox < 1.4.0"],"patched":["github.com/googleapis/mcp-toolbox 1.4.0"],"published":"2026-06-18","updated":"2026-06-19","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-8fcc-w5hv-4gxv","references":[{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-11717"},{"url":"https://github.com/googleapis/mcp-toolbox/pull/3341"},{"url":"https://github.com/advisories/GHSA-8fcc-w5hv-4gxv"}],"tags":["ghsa","go"],"epss":0.00176,"epssPercentile":0.07426,"ingestedAt":"2026-06-29T14:31:46.958Z","slug":"CVE-2026-11717","body":"## Overview\n\nAn 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.\n\n## Affected packages\n\n- `github.com/googleapis/mcp-toolbox < 1.4.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `github.com/googleapis/mcp-toolbox 1.4.0`","depth":"midnight","depthScore":52,"depthScoreParts":{"impact":52.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}