CVE-2026-90898

Bifrost unauthenticated remote code execution via MCP stdio client registration

State: Published
Severity: 9.8 Critical
Published: Sep 14, 2026
Updated: Sep 14, 2026
Reserved: Sep 14, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	9.8 Critical	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H	JFROG

Weaknesses

CWE-306 Missing Authentication for Critical Function
CWE-284 Improper Access Control

Affected Products

Product	Versions
Bifrostmaximhq	before 2.1.0Affected

References

PR #6757: refuse unauthenticated stdio MCP registrationpatch
Merge commit for PR #6757patch
Bifrost HTTP v2.1.0 (first release containing the fix)release-notes
Bifrost repositoryproduct

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