Paper/Archive/CVE-2026-90898

CVE-2026-90898

maximhq Bifrost — Bifrost unauthenticated remote code execution via MCP stdio client registration

CVSS 9.8 (CNA)9.8 / 10 × 3029.4 Not in CISA KEV+300.0 EPSS percentile 83.4.834 × 2016.7 No public exploit+100.0 SSVC exploitation: none+100.0

Description · from the CVE record

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

ProductAffectedFixed inSource

Bifrost< 2.1.02.1.0CNA

Scores by source

JFROG (CNA)9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

patchgithub.com/maximhq/bifrost/pull/6757 patchgithub.com/maximhq/bifrost/commit/12e170352bd25eab1ae9ba16611f1797d1fd8fdc refgithub.com/maximhq/bifrost/releases/tag/transports/v2.1.0 refgithub.com/maximhq/bifrost