CVE-2020-25201 in Consul Enterprise
Summary
by MITRE • 11/05/2020
HashiCorp Consul Enterprise version 1.7.0 up to 1.8.4 includes a namespace replication bug which can be triggered to cause denial of service via infinite Raft writes. Fixed in 1.7.9 and 1.8.5.
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Analysis
by VulDB Data Team • 12/02/2020
HashiCorp Consul Enterprise versions 1.7.0 through 1.8.4 contain a critical namespace replication vulnerability that manifests as an infinite Raft write loop, leading to denial of service conditions. This flaw exists within the distributed consensus mechanism that governs cluster state synchronization across multiple nodes. The vulnerability specifically affects the namespace replication functionality where the system enters an infinite loop during the Raft consensus process when handling namespace-related operations. The bug is triggered when the system attempts to replicate namespace configurations between cluster nodes, causing continuous Raft write operations that consume excessive system resources and ultimately render the affected nodes unresponsive.
The technical implementation of this vulnerability stems from improper state management within the Raft consensus protocol implementation. When namespace replication occurs, the system fails to properly terminate the replication loop, causing it to continuously attempt to write the same namespace state information to the Raft log. This creates a feedback loop where each Raft write operation triggers additional replication attempts, exponentially increasing system load. The issue is particularly severe because Raft consensus is fundamental to Consul's operation, making the denial of service impact widespread across the entire cluster. The vulnerability directly maps to CWE-835, which addresses infinite loops in software implementations, and represents a classic example of a resource exhaustion attack vector.
The operational impact of this vulnerability extends beyond simple service disruption to encompass complete cluster instability. Affected Consul Enterprise clusters experience progressive degradation of performance metrics, with CPU utilization and memory consumption reaching critical levels. Network bandwidth consumption increases dramatically as the infinite Raft write operations generate excessive network traffic between cluster nodes. The denial of service condition can persist for extended periods until manual intervention occurs or the system reaches resource exhaustion. This vulnerability particularly affects enterprise environments where Consul is used for service discovery, configuration management, and mesh networking, potentially disrupting critical infrastructure operations. Organizations relying on Consul for mission-critical applications face significant risk of service outages and operational disruptions.
The recommended mitigation strategy involves immediate deployment of HashiCorp Consul Enterprise version 1.7.9 or 1.8.5, which contain the necessary patches to resolve the namespace replication loop. System administrators should conduct thorough testing of the patched versions in staging environments before production deployment to ensure compatibility with existing configurations. Network monitoring should be enhanced to detect unusual Raft write patterns that may indicate the vulnerability's exploitation. Organizations should also implement automated alerting mechanisms that trigger when Raft write rates exceed normal operational thresholds. From an ATT&CK framework perspective, this vulnerability aligns with T1499.004, which covers network disruption techniques, and represents a sophisticated attack vector that leverages legitimate system functionality to create denial of service conditions. Regular security assessments and vulnerability scanning should be implemented to identify similar issues in other distributed systems components that may be susceptible to similar consensus mechanism flaws.