CVE-2026-59818 in etcd
Summary
by MITRE • 07/09/2026
etcd is a distributed key-value store for the data of a distributed system. Prior to 3.5.32 and 3.6.13, when etcd is configured with --listen-client-http-urls to split HTTP and gRPC client endpoints onto separate listeners, the --client-crl-file Certificate Revocation List is not enforced on the gRPC listener, allowing a client with a revoked certificate to authenticate successfully over gRPC. This issue is fixed in versions 3.5.32 and 3.6.13.
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Analysis
by VulDB Data Team • 07/09/2026
The vulnerability in etcd affects versions prior to 3.5.32 and 3.6.13 where the security configuration fails to enforce Certificate Revocation List validation across all client endpoints. This represents a critical flaw in the authentication mechanism that undermines the integrity of the distributed key-value store system. When administrators configure etcd with separate HTTP and gRPC listeners using the --listen-client-http-urls parameter, they expect consistent security policies to be applied across both interfaces. The failure to validate client certificates against the Certificate Revocation List (CRL) on the gRPC endpoint creates a persistent security gap that allows compromised or revoked certificates to bypass authentication mechanisms.
This vulnerability stems from an inconsistent implementation of certificate validation logic within etcd's authentication subsystem where the --client-crl-file parameter is properly enforced on HTTP listeners but ignored on gRPC listeners. The technical flaw manifests as a missing check in the gRPC authentication flow that should validate client certificates against the configured CRL file before granting access to the distributed system. This inconsistency creates a scenario where an attacker could obtain a revoked certificate and successfully authenticate over gRPC connections while being properly rejected over HTTP connections, effectively creating a bypass mechanism for unauthorized access.
The operational impact of this vulnerability is significant for organizations relying on etcd for critical distributed system coordination and configuration management. A successful exploitation would allow attackers to gain unauthorized access to the key-value store, potentially leading to data manipulation, service disruption, or privilege escalation within the distributed environment. The vulnerability affects systems where certificate-based authentication is implemented using CRL validation as a security control, making it particularly dangerous in environments where certificate lifecycle management is critical for maintaining system security posture.
Organizations should immediately upgrade to etcd versions 3.5.32 or 3.6.13 where this issue has been resolved through proper enforcement of CRL validation across all client endpoints. The fix ensures consistent application of certificate revocation policies regardless of whether clients connect via HTTP or gRPC interfaces, maintaining the security guarantees that administrators expect from certificate-based authentication systems. Security teams should also review existing certificate management practices and ensure that CRL files are properly maintained and distributed to prevent unauthorized access through compromised certificates.
This vulnerability aligns with CWE-295 which addresses improper certificate validation and relates to ATT&CK technique T1566 for credential access through network infiltration. The flaw demonstrates the importance of consistent security policy enforcement across all system interfaces and highlights the critical need for comprehensive testing of authentication mechanisms in distributed systems where multiple protocols are supported simultaneously. Organizations should implement continuous monitoring to detect unauthorized access attempts and maintain robust certificate lifecycle management processes that include regular CRL updates and certificate revocation verification procedures.