Risk Letters

Exploited vulnerability

CVE-2026-90898

TLP:CLEAR

Improper Access Control

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

Facts

  • Vendor: maximhq
  • Product: Bifrost registers
  • CVSS: 9.8
  • EPSS (probability of exploitation within 30 days): 2.3 %
  • First known exploitation: 23 October 2026
  • First seen by Risk Letters: 14 September 2026

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Data: NVD (public domain), CISA KEV, FIRST EPSS, MITRE ATT&CK, AlienVault OTX. NVD