{"id":"CVE-2026-103091","state":"PUBLISHED","title":"Insecure Default Policy and Unrestricted OIDC Enrollment in Google OSS Agent Mesh (SAM)","description":"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.","publishedAt":"2026-10-19T02:24:35.225Z","updatedAt":"2026-10-19T17:44:31.625Z","severity":{"score":9.3,"label":"Critical","version":"4.0","vector":"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","source":"Google"},"assigner":"Google","products":["Google SAM"],"affected":[{"vendor":"Google","product":"SAM","packageName":"github.com/google/sam","defaultStatus":"unaffected","versions":[{"version":"0.1.0-alpha.1","status":"affected","lessThan":"0.1.0-alpha.9","versionType":"semver"}]}],"references":["https://github.com/google/sam/security/advisories/GHSA-cgmg-9xf6-rrgw","https://github.com/google/sam/releases/tag/v0.1.0-alpha.9","https://github.com/google/agentmesh/security/advisories/GHSA-cgmg-9xf6-rrgw"],"weaknesses":["CWE-862","CWE-1188","CWE-306","CWE-863","CWE-200"],"ingestedAt":"2026-10-29T20:10:23.711Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/103xxx/CVE-2026-103091.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-103091","state":"PUBLISHED","datePublished":"2026-10-19T02:24:35.225Z","dateUpdated":"2026-10-19T17:44:31.625Z","assignerShortName":"Google","assignerOrgId":"14ed7db2-1595-443d-9d34-6215bf890778","dateReserved":"2026-09-30T01:36:24.048Z"},"containers":{"cna":{"title":"Insecure Default Policy and Unrestricted OIDC Enrollment in Google OSS Agent Mesh (SAM)","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Google","product":"SAM","packageName":"github.com/google/sam","defaultStatus":"unaffected","versions":[{"version":"0.1.0-alpha.1","status":"affected","lessThan":"0.1.0-alpha.9","versionType":"semver"}]}],"references":[{"url":"https://github.com/google/sam/security/advisories/GHSA-cgmg-9xf6-rrgw","tags":["vendor-advisory"]},{"url":"https://github.com/google/sam/releases/tag/v0.1.0-alpha.9","tags":["release-notes"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"HIGH","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"HIGH","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"CRITICAL","baseScore":9.3,"vectorString":"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"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-862","lang":"en","description":"CWE-862 Missing Authorization","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-1188","lang":"en","description":"CWE-1188 Initialization of a Resource with an Insecure Default","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-306","lang":"en","description":"CWE-306 Missing Authentication for Critical Function","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-863","lang":"en","description":"CWE-863 Incorrect Authorization","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-200","lang":"en","description":"CWE-200 Exposure of Sensitive Information to an Unauthorized Actor","type":"CWE"}]}],"providerMetadata":{"shortName":"Google","orgId":"14ed7db2-1595-443d-9d34-6215bf890778","dateUpdated":"2026-10-19T02:24:35.225Z"},"datePublic":"2026-09-06T16:01:00.000Z","impacts":[{"capecId":"CAPEC-180","descriptions":[{"lang":"en","value":"CAPEC-180 Exploiting Incorrectly Configured Access Control Security Levels"}]},{"capecId":"CAPEC-122","descriptions":[{"lang":"en","value":"CAPEC-122 Privilege Abuse"}]}],"credits":[{"lang":"en","value":"Eli Ainhorn (Noma Security)","type":"finder"}],"source":{"discovery":"EXTERNAL"},"x_generator":{"engine":"Vulnogram 1.0.2"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/google/agentmesh/security/advisories/GHSA-cgmg-9xf6-rrgw","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-19T17:43:50.321526Z","id":"CVE-2026-103091","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T17:44:31.625Z"}}]}}}