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CVE-2026-103091— Insecure Default Policy and Unrestricted OIDC Enrollment in Google OSS Agent Mesh (SAM)

Quick assessment

Affected
Google SAM
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Google OSS Agent Mesh (SAM) 的 0.1.0-alpha.1 至 0.1.0-alpha.8 版本中，MCP 代理（ 中的 函数）以及 OIDC 注册流程（ 中的 和 端点）存在“缺少授权”（CWE-862）和“使用不安全的默认值初始化资源”（CWE-1188）漏洞。该漏洞允许远程攻击者自行注册加入服务网格，并在所有已连接的 MCP 后端节点上调用任意工具。 具体而言，由于 接口公开披露了 OIDC 配置信息，而 接口在缺少声明过滤和黑名单检查的情况下，会自动为任何持有有效 OIDC

CVSS 9.3 · Critical
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I. Basic Information for CVE-2026-103091

Vulnerability Information
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Vulnerability Title
Insecure Default Policy and Unrestricted OIDC Enrollment in Google OSS Agent Mesh (SAM)
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Google SAM 0.1.0-alpha.1 ~ 0.1.0-alpha.9 -

II. Public POCs for CVE-2026-103091

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III. Intelligence Information for CVE-2026-103091

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IV. Related Vulnerabilities

Same product: SAM
Same vendor: Google
Same weakness: CWE-862

V. Comments for CVE-2026-103091

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