CVE-2018-3825 in Elastic Cloud Enterprise
Summary
by MITRE
In Elastic Cloud Enterprise (ECE) versions prior to 1.1.4 a default master encryption key is used in the process of granting ZooKeeper access to Elasticsearch clusters. Unless explicitly overwritten, this master key is predictable across all ECE deployments. If an attacker can connect to ZooKeeper directly they would be able to access configuration information of other tenants if their cluster ID is known.
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Analysis
by VulDB Data Team • 03/25/2020
Elastic Cloud Enterprise version 1.1.4 and earlier contains a critical cryptographic vulnerability that undermines the security isolation between tenant deployments within the platform. This vulnerability stems from the use of a hardcoded default master encryption key that is shared across all ECE installations, creating a predictable cryptographic weakness that directly violates fundamental security principles of isolation and confidentiality. The flaw exists specifically in the process of granting ZooKeeper access to Elasticsearch clusters, where the system fails to generate unique cryptographic keys for each deployment, leaving all tenants vulnerable to cross-tenant information disclosure.
The technical implementation of this vulnerability involves the predictable nature of the default master encryption key that is embedded within the ECE software distribution. When ECE initializes its cluster configuration, it defaults to using this well-known key rather than generating a unique cryptographic identifier for each installation. This design flaw creates a situation where any attacker with network access to the ZooKeeper service can leverage the predictable key to decrypt and access configuration data from other tenant clusters. The vulnerability is particularly concerning because it does not require complex exploitation techniques or privileged access within the ECE environment itself, making it accessible to attackers who can establish direct network connections to the ZooKeeper service.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass potential privilege escalation and lateral movement within multi-tenant deployments. When an attacker successfully accesses another tenant's cluster configuration through the predictable encryption key, they gain access to sensitive metadata including cluster identifiers, resource allocations, and potentially credential information that could facilitate further attacks. This represents a violation of the principle of least privilege and undermines the core security model of multi-tenant cloud platforms. The vulnerability affects all ECE deployments that have not explicitly overridden the default encryption key, creating a widespread risk across organizations that have not implemented proper cryptographic key management practices.
Organizations affected by this vulnerability should immediately implement mitigations including explicit key rotation and the deployment of unique encryption keys for each ECE installation. The recommended approach involves configuring custom master encryption keys through the ECE configuration parameters before any new deployments or upgrades occur. Additionally, network segmentation and access controls should be implemented to restrict direct access to ZooKeeper services from unauthorized networks. From a compliance perspective, this vulnerability would be classified under CWE-327 (Use of a Broken or Risky Cryptographic Algorithm) and could be leveraged by attackers following techniques described in the MITRE ATT&CK framework under T1071.3 (Application Layer Protocol: Dns) and T1046 (Network Service Scanning) to discover and exploit the vulnerable ZooKeeper endpoints. The vulnerability demonstrates the critical importance of proper cryptographic key management and the dangers of relying on default configurations in security-sensitive environments.