Is CVE-2026-90898 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-90898?

CVE-2026-90898 has a CVSS v3 severity of CRITICAL (9.8).

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CVE-2026-90898

Description

Bifrost registers MCP clients through its management API. A stdio client is a command plus args. Bifrost starts that program in the gateway the moment the client is added. No MCP handshake required. The default is governance.auth_config.is_enabled=false. Auth off means every caller is a local admin. One unauthenticated POST /api/mcp/client is enough to run a program as the Bifrost process user (appuser on the official image). transports/v2.1.0 refuses an unauthenticated stdio registration with 403. transports/v2.0.0 still allows it.