ESPv2 vulnerable to JWT authentication bypass via `X-HTTP-Method-Override` header

ESPv2 is a service proxy that provides API management capabilities using Google Service Infrastructure. ESPv2 2.20.0 through 2.42.0 contains an authentication bypass vulnerability. API clients can craft a malicious X-HTTP-Method-Override header value to bypass JWT authentication in specific cases.

ESPv2 allows malicious requests to bypass authentication if both the conditions are true: The requested HTTP method is not in the API service definition (OpenAPI spec or gRPC google.api.http proto annotations, and the specified X-HTTP-Method-Override is a valid HTTP method in the API service definition. ESPv2 will forward the request to your backend without checking the JWT. Attackers can craft requests with a malicious X-HTTP-Method-Override value that allows them to bypass specifying JWTs. Restricting API access with API keys works as intended and is not affected by this vulnerability.

Upgrade deployments to release v2.43.0 or higher to receive a patch. This release ensures that JWT authentication occurs, even when the caller specifies x-http-method-override. x-http-method-override is still supported by v2.43.0+. API clients can continue sending this header to ESPv2.