anonhaven

CVE-2026-90898

CRITICAL CVSS 3.1: 9.8 EPSS 0.62%
Updated Sep 18, 2026
Bifrost
Parameter Value
CVSS 9.8 (CRITICAL)
Type CWE-306 (Missing Authentication for Critical Function), CWE-284 (Improper Access Control)
Vendor Bifrost
Public PoC No

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.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service

CVSS Vector v3.1

Weakness Type (CWE)

CWE-306 Missing Authentication for Critical Function
CWE-284 Improper Access Control

References 4

https://github.com/maximhq/bifrost
reefs@jfrog.com
https://github.com/maximhq/bifrost/commit/12e170352bd25eab1ae9ba16611f1797d1fd8…
reefs@jfrog.com
https://github.com/maximhq/bifrost/pull/6757
reefs@jfrog.com
https://github.com/maximhq/bifrost/releases/tag/transports/v2.1.0
reefs@jfrog.com
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