CVE-2025-61734 is a vulnerability identified in Apache Kylin, an open-source distributed analytics engine designed to provide a SQL interface and multi-dimensional analysis (OLAP) on Hadoop and other big data platforms. The vulnerability is categorized under CWE-552, which refers to files or directories being accessible to external parties without proper authorization. This means that certain files or directories within Apache Kylin versions 4.0.0 through 5.0.2 could be accessed by unauthorized users, potentially exposing sensitive data or configuration files. The vulnerability arises due to insufficient access control mechanisms protecting these resources. The advisory notes that the risk is mitigated if the system and project administrator access controls are robustly enforced, implying that the vulnerability primarily affects environments where administrative protections are weak or misconfigured. The issue was addressed in Apache Kylin version 5.0.3, which includes fixes to restrict unauthorized access to these files or directories. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability was published on October 2, 2025, and the Apache Software Foundation is the vendor responsible for the product and the fix.

For European organizations utilizing Apache Kylin, this vulnerability poses a risk of unauthorized data exposure. Given that Apache Kylin is often deployed in big data analytics environments, unauthorized access to files or directories could lead to leakage of sensitive business intelligence data, configuration details, or credentials stored within the system. This could compromise confidentiality and potentially integrity if attackers modify accessible files. The impact is particularly significant for organizations relying on Kylin for critical analytics workloads, such as financial institutions, telecommunications, and government agencies, where data sensitivity is high. Additionally, unauthorized access could facilitate further lateral movement within the network if attackers leverage exposed information. However, the vulnerability requires that administrative access controls be weak or misconfigured, so organizations with strong access management may be less affected. The absence of known exploits reduces immediate risk but does not eliminate the potential for future attacks, especially as threat actors often target big data platforms for valuable insights. Overall, the vulnerability could undermine trust in data confidentiality and disrupt analytics operations if exploited.

European organizations should prioritize upgrading Apache Kylin to version 5.0.3 or later, which contains the official fix for this vulnerability. Beyond patching, organizations should audit and strengthen access controls around Kylin administrative interfaces and file system permissions to ensure that only authorized personnel have access. Implement network segmentation to isolate Kylin servers from general user networks and restrict access via firewalls or access control lists. Conduct regular security reviews and penetration testing focused on file and directory permissions within Kylin deployments. Employ monitoring and alerting for unusual access patterns to sensitive files or directories. Additionally, encrypt sensitive data at rest within the Kylin environment to reduce the impact of unauthorized access. Document and enforce strict operational procedures for managing Kylin administrative credentials and access rights. Finally, maintain an inventory of all Kylin instances and ensure consistent patch management practices across the organization.