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41Track*

Unauthenticated command execution in Bifrost MCP registration

maximhq Bifrost · CVE-2026-90898 ETK-2026-2538 EUVD-2026-77357 GHSA-GQJQ-CGXR-8C7C
0 news outlets0 CERTs and agencies1 research labs

Assessment: Track*

SSVC decision points: exploitation poc, automatable yes, technical impact total, deployment low.

What is it?

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.

Evidence

Technical advisories1Detailed write-ups from security research teams

Exploitation

  • Public proof of concept
  • Exploited in the wild
  • Listed as known exploited
CVSS
9.8
EPSS
2.3%
First seen
1 h ago
Status
confirmed

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