Unauthenticated MCP Client Registration in Bifrost by Maximhq
CVE-2026-90898

9.8CRITICAL

Key Information:

Vendor

Maximhq

Status
Bifrost
Vendor
CVE Published:
14 September 2026

Badges

👾 Exploit Exists

What is CVE-2026-90898?

The vulnerability in Bifrost allows malicious users to register an MCP client through the management API without authentication. By exploiting this flaw, an attacker can issue an unauthenticated POST request to the /api/mcp/client endpoint, allowing them to execute commands as the Bifrost process user. This could lead to unauthorized actions within the system. Notably, the issue was remedied in transports v2.1.0, which denies unauthenticated registrations, while v2.0.0 is still susceptible. Users are advised to upgrade to the latest version to mitigate this risk.

Affected Version(s)

Bifrost Linux 0 < 2.1.0

References

https://github.com/maximhq/bifrost/pull/6757
patch
https://github.com/maximhq/bifrost/commit/12e170352bd25ea...
patch
https://github.com/maximhq/bifrost/releases/tag/transport...
release-notes

CVSS V3.1

Score:
9.8
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

Yuval Moravchick | JFrog
.