A significant security vulnerability has been identified in Splunk Universal Forwarder for Windows, potentially allowing non-administrator users to access and modify critical system files. This flaw, designated as CVE-2025-20298 with a CVSSv3.1 score of 8.0, poses a substantial risk to organizations utilizing Splunk’s data forwarding capabilities.
Understanding the Vulnerability
The core issue lies in improper permission assignments during the installation or upgrade processes of Splunk Universal Forwarder on Windows systems. Specifically, versions prior to 9.4.2, 9.3.4, 9.2.6, and 9.1.9 are affected. During these processes, the installation directory—typically located at `C:\Program Files\SplunkUniversalForwarder`—is assigned permissions that inadvertently allow non-administrator users to access and modify its contents.
This misconfiguration is categorized under CWE-732 (Incorrect Permission Assignment for Critical Resource), highlighting a fundamental lapse in access control mechanisms. The CVSSv3.1 vector for this vulnerability is CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H, indicating that while exploitation requires low-level privileges and user interaction, it can have a high impact on confidentiality, integrity, and availability. The network attack vector component suggests potential for remote exploitation under certain conditions.
Impacted Versions and Scope
The vulnerability affects multiple versions across several release branches of Splunk Universal Forwarder for Windows:
– 9.4 branch: Versions prior to 9.4.2
– 9.3 branch: Versions prior to 9.3.4
– 9.2 branch: Versions prior to 9.2.6
– 9.1 branch: Versions prior to 9.1.9
This extensive range indicates that numerous enterprise deployments may be susceptible to this security flaw.
Potential Security Implications
For organizations utilizing Splunk Universal Forwarder to collect and forward sensitive log data from Windows systems, this vulnerability presents several risks:
– Unauthorized Data Access: Non-administrator users could gain access to configuration files and forwarded data, leading to potential data breaches.
– Data Integrity Compromise: Malicious actors might modify configuration or log files, undermining the reliability of audit trails and compliance records.
– Service Disruption: Alterations to forwarding behavior could disrupt monitoring services, affecting the organization’s ability to detect and respond to incidents promptly.
Mitigation Strategies
To address this vulnerability, Splunk recommends the following actions:
1. Immediate Upgrade: Organizations should upgrade to the fixed versions: 9.4.2, 9.3.4, 9.2.6, 9.1.9, or higher. Given the high severity rating, prioritizing these updates is crucial.
2. Temporary Workaround: If immediate upgrading is not feasible, a mitigation command can be executed as a Windows system administrator. This involves running the following `icacls.exe` command from a command prompt or PowerShell window:
“`shell
icacls C:\Program Files\SplunkUniversalForwarder /inheritance:r /grant:r Administrators:(OI)(CI)F SYSTEM:(OI)(CI)F
“`
This command removes the problematic permissions, restricting access to the installation directory to administrators and the system account only.
Conclusion
The discovery of CVE-2025-20298 underscores the importance of stringent access control configurations during software installations and upgrades. Organizations relying on Splunk Universal Forwarder for Windows must take immediate action to mitigate this vulnerability by upgrading to the recommended versions or applying the provided workaround. Ensuring that only authorized personnel have access to critical system directories is essential for maintaining the integrity and security of enterprise environments.
