{"id":"CVE-2026-103091","title":"Insecure Default Policy and Unrestricted OIDC Enrollment in Google OSS Agent Mesh (SAM)","summary":"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/contro…","severity":"critical","cvss":9.3,"cvssVector":"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","cvssSource":"cna","cwe":["CWE-862","CWE-1188","CWE-306","CWE-863","CWE-200"],"vendor":"Google","product":"github.com/google/sam","affected":["github.com/google/sam >= 0.1.0-alpha.1 < 0.1.0-alpha.9"],"published":"2026-10-19","updated":"2026-10-19","sourceUpdated":"2026-10-19T02:24:35.225Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-103091","references":[{"url":"https://github.com/google/sam/security/advisories/GHSA-cgmg-9xf6-rrgw"},{"url":"https://github.com/google/sam/releases/tag/v0.1.0-alpha.9"}],"tags":["cve.org"],"ingestedAt":"2026-10-19T02:58:59.957Z","slug":"CVE-2026-103091","body":"## Overview\n\nMissing 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.\n\n## Affected\n\n- `github.com/google/sam >= 0.1.0-alpha.1 < 0.1.0-alpha.9`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":51,"depthScoreParts":{"impact":51.2,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}