How to meet it
OWASP AISVS v1.01
Model Context Protocol (MCP) Security · Secure Transport
Check Origin and Host headers
Verify that MCP servers validate both the Origin header and the Host header independently on all HTTP-based transports to prevent DNS rebinding attacks.
OWASP AISVS v1.01, requirement 10.3.3
In plain English
Check both the Origin and Host headers on HTTP-based MCP servers, to stop DNS rebinding attacks from web pages.
What good looks like
- Origin is checked against an allow-list.
- Host is checked separately.
- Local servers bind to localhost only.
How teams usually do it
- Middleware validating both headers.
Evidence an auditor would accept
- Tests with spoofed Origin and Host values.
Common mistakes
- Checking only one of the two headers.
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Requirement text from the OWASP AI Security Verification Standard, licensed under CC BY-SA 4.0. This guidance is shared under the same licence.