CVE-2025-20298 is a high-severity vulnerability affecting Splunk Universal Forwarder for Windows versions prior to 9.4.2, 9.3.4, 9.2.6, and 9.1.9. The vulnerability arises from improper permission settings on the Universal Forwarder installation directory (default path: C:\Program Files\SplunkUniversalForwarder) during new installations or upgrades to affected versions. Specifically, the directory and its contents are assigned permissions that allow non-administrator local users to read or modify files within this critical directory. This misconfiguration can lead to unauthorized access or tampering with security-critical resources used by the Universal Forwarder, which is a lightweight agent designed to collect and forward log data to Splunk servers for analysis. The CVSS 3.1 score of 8.0 reflects the vulnerability's network attack vector (AV:N), low attack complexity (AC:L), requirement for low privileges (PR:L), and user interaction (UI:R). The impact includes high confidentiality, integrity, and availability consequences, as unauthorized users could potentially manipulate log forwarding configurations, inject malicious data, or disrupt logging operations. Although no known exploits are currently reported in the wild, the vulnerability's characteristics make it a significant risk, especially in environments where multiple users have local access to the same machine. The vulnerability was reserved in October 2024 and published in June 2025, indicating recent discovery and disclosure. The lack of available patches at the time of this report underscores the urgency for organizations to apply updates once released or implement interim mitigations.

For European organizations, the impact of CVE-2025-20298 can be substantial, particularly in sectors relying heavily on Splunk Universal Forwarder for security monitoring, compliance, and operational intelligence. Unauthorized access to the Universal Forwarder directory could allow malicious insiders or local attackers to alter log data, potentially masking their activities or injecting false information. This undermines the integrity of security monitoring and incident response processes, increasing the risk of undetected breaches. Additionally, disruption or manipulation of log forwarding can affect availability of critical security data, impeding compliance with regulations such as GDPR, NIS Directive, and other data protection laws prevalent in Europe. Organizations with shared workstations or environments where multiple users have local access are especially vulnerable. The vulnerability also poses a risk to the confidentiality of sensitive log data, which may contain personal or proprietary information. Given the high CVSS score and the critical role of Splunk in security operations, exploitation could lead to significant operational and reputational damage.

European organizations should prioritize upgrading Splunk Universal Forwarder for Windows to versions 9.4.2, 9.3.4, 9.2.6, or 9.1.9 as soon as these patches become available. Until patches are applied, organizations should implement strict local access controls to limit the number of users with local access to machines running the Universal Forwarder. Employing application whitelisting and monitoring file system permissions on the installation directory can help detect unauthorized changes. Additionally, organizations should audit and harden the permissions of the Universal Forwarder installation directory manually, ensuring only administrators and the Splunk service account have read/write access. Monitoring logs for unusual activity related to the Universal Forwarder and conducting regular integrity checks on configuration files can provide early warning of exploitation attempts. Network segmentation to isolate critical Splunk infrastructure and the use of endpoint detection and response (EDR) tools can further reduce risk. Finally, organizations should review and update incident response plans to address potential exploitation scenarios involving log manipulation or disruption.