---
cve: "CVE-2026-103091"
severity: "CRITICAL"
cvss: 9.3
epss: ""
vendor: "Google"
kev: false
exploited: false
published: "2026-10-19 03:16:58"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-10-22T17:03:09+02:00"
---

# CVE-2026-103091

> 9.3 CRITICAL · 🧪 PoC

## Beschreibung

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.

## CNA-Record (Kanon, cvelistV5)

- CNA: **Google**
- State: PUBLISHED
- Stand: 2026-10-19 17:44:31
- CNA-CVSS: **9.3** (`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`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **poc**
  - Automatable: **no**
  - Technical Impact: **total**

## CVSS-Vektor

```
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
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Schwachstellen-Klasse

- **CWE-862** — Missing Authorization
  The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
- **CWE-1188** — Initialization of a Resource with an Insecure Default
  The product initializes or sets a resource with a default that is intended to be changed by the product's installer, administrator, or maintainer, but the default is not secure.

## Angriffsmuster (CAPEC)

- [CAPEC-665 — Exploitation of Thunderbolt Protection Flaws](https://capec.mitre.org/data/definitions/665.html) _(Severity: Very High)_

## ATT&CK-Techniken

- [T1211 — Exploitation for Defensive Evasion](https://attack.mitre.org/techniques/T1211/)
- [T1542.002 — Pre-OS Boot: Component Firmware](https://attack.mitre.org/techniques/T1542/002/)
- [T1556 — Modify Authentication Process](https://attack.mitre.org/techniques/T1556/)

## Patch verfügbar (OSV)

- bcf9bc22e5f4bb00eb504c1ab5f55815e0e91f23 (Commit)

## Referenzen

- <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>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-103091/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_