---
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'
---

## Overview

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

- `github.com/google/sam >= 0.1.0-alpha.1 < 0.1.0-alpha.9`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.