Chef Automate API Gateway - Authentication Bypass
Chef Automate derives an internal service identity from an X.509 certificate supplied in a request header without verifying its issuer. The load balancer blanks X-Client-Cert but does not strip the Grpc-Metadata- prefixed variants, which grpc-gateway rewrites into the metadata key the gateway's auth middleware reads. A remote unauthenticated attacker can present a self-signed certificate naming an internal service such as deployment-service and be authenticated as that service. References: https://community.progress.com/s/article/Critical-Security-Bulletin---August-2026---Chef-Automate-Security-Vulnerability https://nvd.nist.gov/vuln/detail/CVE-2026-80462 Remediation: Upgrade to Chef Automate 4.13.520 or later, which adds x509 chain verification to the header certificate path and strips the Grpc-Metadata prefixed headers at the load balancer. As an independent mitigation, blank Grpc-Metadata-Grpcgateway-X-Client-Cert, Grpc-Metadata-X-Client-Cert and X-Client-Cert at any proxy in front of Automate, repeating the directives in every location block that proxies to the gateway.
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