CVE-2025-20386 is a vulnerability identified in Splunk Enterprise for Windows versions below 10.0.2, 9.4.6, 9.3.8, and 9.2.10. The issue stems from the product specifying permissions for the Splunk Enterprise installation directory in a manner that inadvertently grants non-administrator users on the local machine read and write access to this security-critical resource. This misconfiguration can occur during a fresh installation or an upgrade to an affected version. The installation directory contains sensitive configuration files, logs, and potentially credentials or tokens used by Splunk Enterprise, making unauthorized access a significant security risk. The vulnerability allows an attacker with limited local privileges to read or modify these files, potentially leading to privilege escalation, data tampering, or disruption of Splunk services. The CVSS 3.1 base score is 8.0, reflecting high severity, with vector metrics indicating network attack vector, low attack complexity, requiring low privileges, user interaction, and impacting confidentiality, integrity, and availability. No known exploits have been reported in the wild yet, but the vulnerability’s nature makes it a critical concern for environments where multiple users share access to the same Windows host running Splunk Enterprise. The root cause is improper ACL (Access Control List) settings on the installation directory, which should be restricted to administrators and the Splunk service account only.

For European organizations, the impact of CVE-2025-20386 can be significant, especially in sectors relying heavily on Splunk Enterprise for security monitoring, log aggregation, and operational intelligence. Unauthorized local users gaining access to the installation directory could read sensitive logs, configuration files, or credentials, leading to data breaches or exposure of internal security information. Modification of these files could allow attackers to manipulate logs, hide malicious activities, or disrupt Splunk’s operation, undermining incident detection and response capabilities. This can result in loss of data integrity, operational downtime, and increased risk of further compromise. Organizations with shared Windows environments or those allowing multiple users on Splunk servers are particularly vulnerable. The breach of confidentiality and integrity could also have regulatory implications under GDPR if personal data is exposed or manipulated. The availability impact could disrupt critical monitoring services, affecting business continuity and security posture.

1. Apply the official patches or upgrade Splunk Enterprise to versions 10.0.2, 9.4.6, 9.3.8, or 9.2.10 or later as soon as they become available from Splunk. 2. Until patches are applied, manually review and tighten NTFS permissions on the Splunk Enterprise installation directory to restrict access exclusively to administrators and the Splunk service account. 3. Limit local user accounts on Splunk Enterprise Windows hosts to trusted personnel only, minimizing the risk of unauthorized access. 4. Implement strict access control policies and regularly audit file system permissions and access logs for anomalies. 5. Use endpoint detection and response (EDR) tools to monitor for suspicious activities related to file access or modification in the Splunk installation path. 6. Educate system administrators and users about the risks of local privilege misuse and enforce least privilege principles. 7. Consider isolating Splunk Enterprise servers from general user environments to reduce exposure. 8. Regularly back up Splunk configuration and data to enable recovery in case of tampering.