CVE-2026-90898: critical vulnerability in maximhq Bifrost
Bifrost unauthenticated remote code execution via MCP stdio client registration
Published
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85Vexday Risk Score
Patch now. It exploitation observed by VulnCheck and has a working public exploit.
ssvc Actcvss 9.8epss 2.3%
from disclosure to weapon9 days
Published on NVDSep 14
1st PoC+9d
VulnCheck+39d
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Affected products
maximhq · Bifrostpublic PoCs found — 1
githubgithub.com/HORKimhab/CVE-2026-90898★ 0⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
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