{"id":"CVE-2026-103091","summary":"Insecure Default Policy and Unrestricted OIDC Enrollment in Google OSS Agent Mesh (SAM)","details":"Missing Authorization (CWE-862) and Initialization of a Resource with an Insecure Default (CWE-1188) in the MCP proxy (HandleStreamPassThrough in mcp_service.go) and OIDC registration flow (GET /info and POST /register in internal/controlplane/server.go) in Google OSS Agent Mesh (SAM) versions 0.1.0-alpha.1 through 0.1.0-alpha.8 allow a remote attacker to self-enroll into the mesh and invoke arbitrary tools across all connected MCP backend nodes. Because GET /info publicly discloses OIDC configuration, POST /register auto-enrolls any valid OIDC token holder without claim filtering or ban checks, and the default policy binds sam:system:authenticated to wildcard services and targets, an attacker can obtain a mesh credential with full read, write, and execution access on backend services. Users should upgrade to version 0.1.0-alpha.9 or later, which enforces a fail-closed default policy, explicit policy-binding requirements on enrollment, and ban checks.","aliases":["GHSA-cgmg-9xf6-rrgw"],"modified":"2026-10-21T02:54:30.174876123Z","published":"2026-10-19T02:24:35.225Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/103xxx/CVE-2026-103091.json","cna_assigner":"Google","cwe_ids":["CWE-1188","CWE-200","CWE-306","CWE-862","CWE-863"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/103xxx/CVE-2026-103091.json"},{"type":"EVIDENCE","url":"https://github.com/google/agentmesh/security/advisories/GHSA-cgmg-9xf6-rrgw"},{"type":"ADVISORY","url":"https://github.com/google/sam/releases/tag/v0.1.0-alpha.9"},{"type":"ADVISORY","url":"https://github.com/google/sam/security/advisories/GHSA-cgmg-9xf6-rrgw"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-103091"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/google/agentmesh","events":[{"introduced":"ffc3e6072383ea6e9cf3fbadc7cf473db448b364"},{"fixed":"bcf9bc22e5f4bb00eb504c1ab5f55815e0e91f23"}],"database_specific":{"extracted_events":[{"source":"AFFECTED_FIELD","strategy":"StandardRange","range":[{"introduced":"0.1.0-alpha.1"},{"fixed":"0.1.0-alpha.9"}]},{"range":[{"fixed":"bcf9bc22e5f4bb00eb504c1ab5f55815e0e91f23"}],"source":"REFERENCES_TAG","original_tag":"v0.1.0-alpha.9"}]}}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-103091.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"}]}