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CVE-2026-90898

Bifrost unauthenticated remote code execution via MCP stdio client registration

CVSS 3.1 9.8 CRITICALCheck source for fixed versionsKEV status unknown
Original advisory

cve-program · CVE-2026-90898

Published

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.

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Affected versions, risk and source history

Exploitation and risk

Source status

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cve-program · CVE-2026-90898

Published

Bifrost unauthenticated remote code execution via MCP stdio client registration

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.

Source published
14 Sep 2026 10:18:53 UTC
Source modified
14 Sep 2026 11:19:46 UTC
Saved here
23 Oct 2026 15:48:27 UTC
Source terms
CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 3.1 · 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

ChangeIntel

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Sources read 13 Nov 17:25 UTC · 274 of 275 readable · 273 fully read · documentation 469/469 current

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