CVE-2026-55678
MediumCVSS 6.9Exploitation Probability (EPSS)
Low risk32th percentile - higher than 32% of all known CVEs
Summary
Arc Enterprise versions 26.02.1 through 26.06.2 accept cluster join requests without authentication when clustering is enabled but no shared secret is configured. An attacker can become a trusted node, intercept requests, and alter cluster membership.
Risk Assessment
An unauthenticated attacker can intercept authentication headers, query data, and operational metadata, as well as disrupt cluster operations, leading to confidentiality and integrity breaches of telemetry data.
Recommendation
Upgrade Arc Enterprise to version 26.06.2 or later. If not possible, configure cluster.shared_secret for all cluster deployments and ensure cluster.enabled is false in default configurations.
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Original NVD description (English source)
Arc is an open, SQL-native time-series database for telemetry. From 26.02.1 until 26.06.2, Arc Enterprise clustering accepts cluster join requests without authentication when cluster.enabled is true but cluster.shared_secret is not configured. The defaults in internal/config/config.go set cluster.enabled to false, cluster.cluster_name to arc-cluster, cluster.coordinator_addr to :9100, cluster.shared_secret to an empty value, and cluster.tls_enabled to false, while cmd/arc/main.go requires cluster.shared_secret only when cluster.replication_enabled is true. JoinRequest in internal/cluster/protocol/messages.go accepts attacker-controlled node_id, role, raft_addr, api_addr, and coord_addr values, plus optional auth_nonce, auth_timestamp, and auth_hmac fields. The join path in internal/cluster/coordinator.go validates HMAC authentication only when the configured shared secret is non-empty and otherwise proceeds after only the cluster-name check. An accepted node is marked healthy, added as a Raft voter or registered locally, and becomes available through internal/cluster/registry.go to the routing logic in internal/cluster/router.go. The forwardRequest path in internal/cluster/router.go builds its target from node.APIAddress and copies Authorization and x-api-key headers with the request, so a rogue node selected for a forwarded query or write can receive authentication headers, request bodies, database and measurement names, and operational metadata. Heartbeat in internal/cluster/protocol/messages.go also lacks HMAC fields, and internal/cluster/coordinator.go updates node state from supplied node_id and state values without authentication. An unauthenticated network attacker who can reach the coordinator port and knows the cluster name can therefore become a trusted cluster node, mutate cluster membership, be submitted as a Raft voter, intercept topology-dependent forwarded requests, divert or forge operations, and blackhole or delay traffic. The default standalone configuration is not reachable because cluster.enabled is false, but Enterprise cluster deployments with clustering enabled and no shared secret are affected. This issue is fixed in version 26.06.2.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

