etcd versions 3.2.x before 3.2.26 and 3.3.x before 3.3.11 are vulnerable to an improper authentication issue when role-based access control (RBAC) is used and client-cert-auth is enabled. If an etcd client server TLS certificate contains a Common Name (CN) which matches a valid RBAC username, a remote attacker may authenticate as that user with any valid (trusted) client certificate in a REST API request to the gRPC-gateway.

References

• https://nvd.nist.gov/vuln/detail/CVE-2018-16886
• etcd-io/etcd#10366
• etcd-io/etcd@0191509
• etcd-io/etcd@bf9d0d8
• https://access.redhat.com/errata/RHSA-2019:0237
• https://access.redhat.com/errata/RHSA-2019:1352
• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-16886
• https://github.com/etcd-io/etcd/blob/1eee465a43720d713bb69f7b7f5e120135fdb1ac/CHANGELOG-3.2.md#security-authentication
• https://github.com/etcd-io/etcd/blob/1eee465a43720d713bb69f7b7f5e120135fdb1ac/CHANGELOG-3.3.md#security-authentication
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JX7QTIT465BQGRGNCE74RATRQLKT2QE4/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UPGYHMSKDPW5GAMI7BEP3XQRVRLLBJKS/
• http://www.securityfocus.com/bid/106540
• https://pkg.go.dev/vuln/GO-2021-0077