Overview
CVE-2025-20381 is a medium severity vulnerability affecting Splunk MCP Server app versions below 0.2.4. This vulnerability allows a user with access to the “run_splunk_query” Model Context Protocol (MCP) tool to bypass the intended SPL command allowlist controls. By embedding SPL commands as sub-searches within their queries, attackers can execute unauthorized actions, potentially compromising the security and integrity of the Splunk environment.
Technical Details
The vulnerability stems from insufficient validation of SPL commands submitted through the “run_splunk_query” MCP tool. The MCP tool is designed to restrict users to a pre-defined set of allowed SPL commands. However, the validation mechanism fails to properly inspect and sanitize sub-searches embedded within the main query. This allows a malicious user to inject arbitrary SPL commands within these sub-searches, effectively bypassing the allowlist and executing commands that should otherwise be restricted.
For example, a user might craft a query like this:
| inputlookup allowed_lookup WHERE field="value" [search index=_audit | head 1 | return $field]In this scenario, even if the `search` command is not explicitly allowed for direct execution, it can be executed within the sub-search (enclosed in brackets), leading to potential information disclosure or system modification depending on the sub-search content.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) score for CVE-2025-20381 is 5.4 (Medium). This score reflects the following characteristics:
- Attack Vector (AV): Network (N) – The vulnerability is exploitable over a network.
- Attack Complexity (AC): High (H) – Exploitation requires specialized knowledge or access to unusual circumstances.
- Privileges Required (PR): Low (L) – An attacker needs only low-level privileges to exploit the vulnerability.
- User Interaction (UI): None (N) – No user interaction is required for exploitation.
- Scope (S): Unchanged (U) – The vulnerability affects only the vulnerable component.
- Confidentiality Impact (C): Low (L) – There is limited disclosure of information assets.
- Integrity Impact (I): Low (L) – Possible modification of data.
- Availability Impact (A): None (N) – There is no impact to availability.
While the CVSS score is medium, the potential for unauthorized actions and the ease with which low-privileged users can exploit the vulnerability make it a significant concern.
Possible Impact
Successful exploitation of CVE-2025-20381 can lead to the following:
- Unauthorized Data Access: Attackers can access sensitive data that they are not authorized to view.
- System Modification: Attackers may be able to modify system configurations or data.
- Log Tampering: Attackers could potentially alter or delete logs, obscuring their activities.
- Privilege Escalation (Potentially): While not a direct escalation, the vulnerability could be a stepping stone to further compromise.
Mitigation and Patch Steps
To mitigate the risk posed by CVE-2025-20381, it is strongly recommended to upgrade to Splunk MCP Server app version 0.2.4 or later. This version contains the necessary fixes to properly validate SPL commands and prevent the sub-search bypass.
- Upgrade Splunk MCP Server: Download and install the latest version of the Splunk MCP Server app from Splunkbase.
- Verify the Upgrade: After the upgrade, ensure that the version is 0.2.4 or later.
- Monitor Logs: Continuously monitor Splunk logs for any suspicious activity related to the “run_splunk_query” MCP tool.
