Missing Authentication for Critical Function in MCP Gateway - #VU139381
Published: July 26, 2026
Vulnerability identifier: #VU139381
CSH Severity: High
CVSS v4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-306
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to gain unauthenticated access to proxied tools and act with the user's stored secrets and OAuth tokens.
The vulnerability exists due to missing authentication for critical function in the /sse and /mcp HTTP endpoints when running the gateway in container mode with an HTTP transport. A remote attacker can send requests without authentication to gain unauthenticated access to proxied tools and act with the user's stored secrets and OAuth tokens.
The issue occurs because the bearer-token authentication middleware is not installed in container mode, and requests without an Origin header are allowed.
Affected software
MCP Gateway
Remediation
Install security update from vendor's website.
MCP Gateway - update to 0.43.1