CVE-2025-20386: 
Splunk Enterprise vulnerability analysis and mitigation

CVE-2025-20386 is an incorrect permission assignment vulnerability (CWE-732) in Splunk Enterprise for Windows that allows non-administrator local users to access the Splunk installation directory and all its contents following a new installation or upgrade. It affects Splunk Enterprise for Windows versions 9.2.0–9.2.9, 9.3.0–9.3.7, 9.4.0–9.4.5, and 10.0.0–10.0.1. The vulnerability was disclosed on December 3, 2025, by Cisco Systems (the CNA for Splunk). CVSS v3.1 scores differ by assessor: NVD rates it 6.5 (Medium) while the CNA rates it 8.0 (High) (Splunk Advisory, NVD).

The root cause is CWE-732 (Incorrect Permission Assignment for Critical Resource): during a fresh installation or upgrade of Splunk Enterprise on Windows, the installer sets overly permissive access controls on the Splunk installation directory, granting read (and potentially write) access to non-administrator OS users. An attacker with a low-privilege local account can browse the installation directory, read configuration files, credentials, certificates, and other sensitive data stored within it. No special tools or complex techniques are required beyond standard Windows file system access. No public proof-of-concept code has been identified (Splunk Advisory, NVD).

Successful exploitation allows a low-privileged local Windows user to read the entire Splunk Enterprise installation directory, which may contain sensitive configuration files, authentication tokens, API keys, TLS certificates, and indexed log data. This represents a significant confidentiality breach and could facilitate lateral movement if credentials or secrets stored in Splunk configuration files are harvested. Integrity and availability are not directly impacted by the permission misconfiguration itself, though write access (if granted) could enable binary replacement or configuration tampering leading to privilege escalation (Splunk Advisory, Security Online).

No public proof-of-concept exploit code has been published, and there is no evidence of in-the-wild exploitation as of the disclosure date (Splunk Advisory). The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. The EPSS score is approximately 0.029% (0.000290), indicating a very low probability of exploitation in the near term. Exploitation requires local access to the Windows host running Splunk Enterprise, limiting the attack surface to insider threats or attackers who have already achieved initial access.

1. Gain local access: Obtain a low-privilege (non-administrator) account on the Windows host running a vulnerable version of Splunk Enterprise (e.g., via phishing, credential reuse, or another vulnerability).
2. Identify Splunk installation directory: Locate the Splunk installation path, typically C:\Program Files\Splunk\ or a custom directory specified during installation.
3. Check directory permissions: Use icacls "C:\Program Files\Splunk" or Windows Explorer to confirm that the current non-admin user has read (or broader) access to the directory due to the misconfigured permissions set during installation or upgrade.
4. Browse and exfiltrate sensitive files: Navigate the directory to access sensitive files such as etc/passwd, etc/system/local/, SSL certificates, authentication tokens, or any indexed data stored under var/lib/splunk/.
5. Harvest credentials or secrets: Extract credentials, API keys, or configuration details from files such as $SPLUNK_HOME/etc/system/local/authentication.conf or inputs.conf to facilitate lateral movement or privilege escalation (Splunk Advisory, Security Online).

• File System: Unexpected access or modification timestamps on files within the Splunk installation directory (e.g., C:\Program Files\Splunk\etc\) by non-administrator accounts; presence of copied Splunk configuration files in user-accessible locations.
• Logs: Windows Security Event Log entries (Event ID 4663) showing non-administrator accounts accessing the Splunk installation directory; Splunk internal logs (splunkd.log) showing unusual configuration reads or authentication attempts using harvested credentials.
• Process: Non-Splunk processes (e.g., cmd.exe, powershell.exe) running under a low-privilege user account accessing files within C:\Program Files\Splunk\.
• Network: Outbound connections from the Splunk host to unexpected external IPs following local access, potentially indicating credential-based lateral movement (Splunk Advisory).

Splunk has released patched versions that correct the installation directory permissions: 9.2.10, 9.3.8, 9.4.6, and 10.0.2. Organizations should upgrade to one of these versions immediately. As an interim measure, administrators should manually audit and correct the ACLs on the Splunk installation directory using icacls to restrict access to SYSTEM and administrator accounts only. Additionally, organizations should review the principle of least privilege for all local Windows accounts on Splunk hosts and monitor for unauthorized file access (Splunk Advisory).

Security media outlets including SecurityOnline, CyberSecurityNews, eSecurity Planet, TechRepublic, and The Hacker News (weekly recap) covered the vulnerability, generally characterizing it as a high-severity local privilege escalation risk requiring prompt patching (Security Online, CyberSecurityNews). Heise and WebProNews also reported on the Splunk December 2025 patch batch, noting the incorrect file permissions issue alongside a companion vulnerability CVE-2025-20387 (Heise). Community sentiment on social platforms (Mastodon, Bluesky) was largely informational, with no significant controversy or researcher debate noted.