CVE-2018-11802 in Solr
Summary
by MITRE
In Apache Solr, the cluster can be partitioned into multiple collections and only a subset of nodes actually host any given collection. However, if a node receives a request for a collection it does not host, it proxies the request to a relevant node and serves the request. Solr bypasses all authorization settings for such requests. This affects all Solr versions prior to 7.7 that use the default authorization mechanism of Solr (RuleBasedAuthorizationPlugin).
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Analysis
by VulDB Data Team • 11/28/2025
The vulnerability described in CVE-2018-11802 represents a critical authorization bypass flaw within Apache Solr's distributed architecture that fundamentally undermines the security controls designed to protect sensitive data and operations. This issue exists in Solr versions prior to 7.7 and specifically affects systems utilizing the default RuleBasedAuthorizationPlugin mechanism, creating a dangerous scenario where unauthorized access can occur through legitimate proxy request pathways. The vulnerability stems from Solr's handling of cross-node requests within its cluster architecture, where nodes must forward requests to other nodes hosting specific collections when they receive requests for data they do not directly contain.
The technical flaw manifests in Solr's proxy request handling mechanism where the system fails to enforce authorization checks when processing forwarded requests between nodes in a distributed cluster. When a node receives a request for a collection it does not host, it automatically proxies that request to the appropriate node that contains the collection data. However, during this proxying process, Solr completely bypasses all configured authorization settings and security policies that would normally be applied to protect access to the collection. This creates a pathway where malicious actors can potentially exploit the proxy mechanism to access collections they would normally be denied access to, effectively circumventing the authorization controls that should govern data access within the distributed system.
The operational impact of this vulnerability is severe and multifaceted, particularly for organizations relying on Solr's distributed capabilities for managing sensitive data. Attackers can leverage this flaw to gain unauthorized access to collections that are protected by authorization rules, potentially exposing confidential information or enabling further exploitation within the system. The vulnerability affects all Solr versions prior to 7.7, meaning that a significant portion of installations would be vulnerable if they are using the default authorization mechanism. This creates a substantial risk for organizations where Solr is used to manage sensitive datasets, as the bypass allows for privilege escalation and unauthorized data access through legitimate cluster communication pathways.
Organizations should implement immediate mitigations including upgrading to Solr version 7.7 or later where this vulnerability has been addressed, and conducting thorough security reviews of existing authorization configurations to identify potential exposure. Additionally, network-level restrictions should be implemented to limit inter-node communication where possible, and organizations should consider implementing additional monitoring to detect unusual proxy request patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-284, which describes improper access control, and represents a clear violation of the principle of least privilege that should govern all distributed systems. From an ATT&CK perspective, this vulnerability maps to privilege escalation techniques and can be leveraged to move laterally within a system, potentially enabling more sophisticated attacks once initial unauthorized access is achieved.