Vulnerability · Published Sep 14, 2026 · Assigned by JFROG
CVE-2026-90898Bifrost unauthenticated remote code execution via MCP stdio client registration
Critical 9.8
In plain English
A critical-severity missing authentication in Bifrost from maximhq. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 2.3% (higher than 83% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei, public proof-of-concept code.
Official 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.
Affected products (as reported)
Weakness: CWE-306, CWE-284 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H