CVE-2026-103091 Insecure Default Policy and Unrestricted OIDC Enrollment in Google OSS Agent Mesh (SAM)
Remote attackers can self-enroll into the mesh and execute arbitrary tools on backend nodes due to insecure default policies and unrestricted OIDC registration.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-103091?
CVE-2026-103091 is a critical missing authorization vulnerability in Google SAM, published on 19 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-103091?
How do I fix CVE-2026-103091?
No fix has been published for CVE-2026-103091 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-103091 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-103091 exists.
Sources
Also known as GHSA-cgmg-9xf6-rrgw, GHSA-qx8v-pq9p-7g7v.