{"id":"CVE-2026-103091","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-103091","generatedAt":"2026-10-28T01:53:23.020Z","title":"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…","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.","published":"2026-10-19T03:16:58.000Z","lastModified":"2026-10-19T21:13:40.000Z","status":"Awaiting Analysis","sourceIdentifier":"cve-coordination@google.com","cvss":{"version":"4.0","score":9.3,"severity":"CRITICAL","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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M"},"cwe":["CWE-200","CWE-306","CWE-862","CWE-863","CWE-1188"],"affected":[],"epss":{"score":0.00642,"percentile":0.50486,"date":"2026-10-26","history":[{"date":"2026-10-19","score":0.00406,"percentile":0.33455}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.64%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"new","label":"New CVE","at":"2026-10-19T03:16:58.000Z","detail":{"score":"9.3","severity":"CRITICAL","publishedAt":"2026-10-19T03:16:58.377Z"},"summary":"New CVE, critical severity (CVSS 9.3)."}],"references":[{"url":"https://github.com/google/sam/releases/tag/v0.1.0-alpha.9","source":"cve-coordination@google.com"},{"url":"https://github.com/google/sam/security/advisories/GHSA-cgmg-9xf6-rrgw","source":"cve-coordination@google.com"},{"url":"https://github.com/google/agentmesh/security/advisories/GHSA-cgmg-9xf6-rrgw","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-103091","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}