CVE-2021-28235

etcd is a distributed key-value store for the data of a distributed system. Prior to versions 3.5.33, 3.6.14, and 3.7.1, a network attacker who can reach an etcd TLS listener can open many TCP connections and never send a ClientHello. In client/pkg/transport/listener_tls.go, each connection handled by tlsListener.acceptLoop spawns a goroutine that blocks indefinitely inside tls.Conn.Handshake() and remains tracked in the pending map. Unbounded goroutine and map growth can exhaust memory in the etcd process, causing loss of availability for the cluster and, when etcd backs Kubernetes, the control plane. This issue is fixed in versions 3.5.33, 3.6.14, and 3.7.1.

etcd is a distributed key-value store for the data of a distributed system. Prior to versions 3.5.33, 3.6.14, and 3.7.1, a user granted READ permission on a single exact key can use the Watch gRPC API with clientv3.WithFromKey() to receive watch events for every key lexicographically greater than or equal to the permitted key. In server/etcdserver/api/v3rpc/watch.go, the open-ended RangeEnd sentinel is rewritten before the RBAC permission check in server/auth/range_perm_cache.go function isRangeOpPermitted, causing the request to be treated as an exact-key watch. Range/Get and DeleteRange requests are not affected, and the issue affects only clusters with authentication enabled. This issue is fixed in versions 3.5.33, 3.6.14, and 3.7.1.

In etcd prior to versions 3.5.32 and 3.6.13, when 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. This allows a client with a revoked certificate to authenticate successfully over gRPC.