CVE-2017-7660 in Solr
Summary
by MITRE
Apache Solr uses a PKI based mechanism to secure inter-node communication when security is enabled. It is possible to create a specially crafted node name that does not exist as part of the cluster and point it to a malicious node. This can trick the nodes in cluster to believe that the malicious node is a member of the cluster. So, if Solr users have enabled BasicAuth authentication mechanism using the BasicAuthPlugin or if the user has implemented a custom Authentication plugin, which does not implement either "HttpClientInterceptorPlugin" or "HttpClientBuilderPlugin", his/her servers are vulnerable to this attack. Users who only use SSL without basic authentication or those who use Kerberos are not affected.
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Analysis
by VulDB Data Team • 12/31/2020
Apache Solr vulnerability CVE-2017-7660 represents a critical security flaw in the distributed search platform's inter-node communication mechanism that leverages public key infrastructure for authentication. This vulnerability stems from insufficient validation of node identities within the Solr cluster architecture, specifically when security features are enabled. The flaw allows attackers to exploit the PKI-based communication system by crafting malicious node names that appear legitimate to the cluster but do not correspond to actual cluster members, creating a man-in-the-middle scenario that can compromise cluster integrity.
The technical implementation of this vulnerability occurs through the manipulation of node identification within the Solr cluster's trust model. When Solr security is enabled with BasicAuth authentication via BasicAuthPlugin or custom authentication plugins, the system fails to properly validate that incoming node requests originate from legitimate cluster members. This weakness enables attackers to create fake node identifiers that bypass the normal cluster membership verification process, effectively allowing unauthorized nodes to masquerade as legitimate cluster members. The vulnerability specifically targets implementations that lack proper HttpClientInterceptorPlugin or HttpClientBuilderPlugin interfaces, which would normally provide additional security layers for validating node authenticity.
The operational impact of this vulnerability extends beyond simple unauthorized access to encompass potential data compromise and cluster disruption. Attackers can exploit this flaw to gain unauthorized access to cluster resources, potentially leading to data exfiltration, index manipulation, or service disruption. The vulnerability is particularly concerning because it operates at the network communication layer, meaning that even if individual node-level protections exist, the attack can bypass these controls by presenting itself as a trusted cluster member. This creates a scenario where attackers can leverage legitimate cluster communication channels to execute unauthorized operations, making detection more difficult.
Organizations using Solr with BasicAuth authentication or custom authentication mechanisms should implement immediate mitigations including upgrading to patched versions of Apache Solr, implementing additional network-level controls, and ensuring that all authentication plugins properly implement HttpClientInterceptorPlugin or HttpClientBuilderPlugin interfaces. The vulnerability aligns with CWE-287, which addresses improper authentication issues in software systems, and represents a specific implementation weakness in the Apache Solr security framework. From an ATT&CK perspective, this vulnerability maps to techniques involving privilege escalation and lateral movement within networked environments, as attackers can use it to establish unauthorized communication channels within the cluster. The risk is compounded when considering that many organizations may not be aware of the specific plugin requirements needed to prevent exploitation, making this vulnerability particularly insidious in environments where security configurations are not rigorously audited.