CVE-2026-22022 is a vulnerability classified under CWE-285 (Improper Authorization) affecting Apache Solr versions 5.3.0 through 9.10.0 when the RuleBasedAuthorizationPlugin is used with certain configurations. The vulnerability stems from insufficiently strict input validation within the plugin's authorization logic, which can allow unauthorized users to access specific Solr APIs that should be restricted. The conditions for exploitation include: (1) use of the RuleBasedAuthorizationPlugin, (2) a configuration specifying multiple roles, (3) permission lists that include predefined rules such as 'config-read', 'config-edit', 'schema-read', 'metrics-read', or 'security-read' but do not include the 'all' permission, and (4) network setups that allow direct, unfiltered HTTP/HTTPS requests to Solr instances. Under these conditions, an attacker can bypass intended access controls and perform unauthorized read or edit operations on Solr configurations, schemas, metrics, or security settings. This can lead to exposure or manipulation of sensitive data and system configurations. The vulnerability does not require user interaction or authentication but does require network access to the Solr service. No public exploits have been reported yet, but the risk remains significant due to the widespread use of Solr in enterprise search and data indexing. Mitigation is straightforward: upgrading to Solr 9.10.1 or later, or modifying the RuleBasedAuthorizationPlugin configuration to include the 'all' permission assigned to an admin or privileged role, effectively tightening access controls and preventing unauthorized API access.

For European organizations, this vulnerability poses a significant risk of unauthorized access to critical Solr APIs, potentially leading to exposure or unauthorized modification of search indexes, configurations, and security settings. This can compromise data confidentiality and integrity, disrupt search services, and undermine trust in data-driven applications. Organizations relying on Solr for enterprise search, e-commerce, or public sector data indexing could face operational disruptions or data breaches. The impact is heightened in sectors with strict data protection regulations such as GDPR, where unauthorized data access can lead to regulatory penalties and reputational damage. Since exploitation requires network access to Solr, organizations with publicly accessible Solr instances or insufficient network segmentation are particularly vulnerable. The absence of authentication requirements for exploitation increases the risk of automated or opportunistic attacks. Overall, the vulnerability threatens the confidentiality and integrity of data managed by Solr deployments across European enterprises and government agencies.

To mitigate CVE-2026-22022, European organizations should: 1) Immediately upgrade Apache Solr to version 9.10.1 or later, where the vulnerability is fixed. 2) Review and audit RuleBasedAuthorizationPlugin configurations to ensure the 'all' predefined permission is included and assigned exclusively to admin or highly privileged roles, thereby enforcing strict access control. 3) Implement network-level protections such as firewalls, reverse proxies, or API gateways to restrict direct, unfiltered access to Solr endpoints, limiting exposure to trusted internal networks or authenticated clients only. 4) Employ monitoring and logging of Solr API access to detect anomalous or unauthorized requests promptly. 5) Conduct penetration testing and security assessments focused on Solr deployments to verify the effectiveness of authorization controls. 6) Educate DevOps and security teams about the risks of misconfigured authorization plugins and the importance of least privilege principles in Solr security configurations. These steps go beyond generic advice by focusing on configuration hardening, network segmentation, and proactive detection tailored to this specific vulnerability.