CVE-2026-20205: Sensitive Information Disclosure in Splunk MCP Server

Note

Executive Summary (Sommaire exécutif)

CVE-2026-20205 is a high-severity (CVSS 7.2) information disclosure vulnerability affecting Splunk MCP Server app versions below 1.0.3. The flaw permits users with access to the _internal index or the mcp_tool_admin capability to view sensitive session and authorization tokens in clear text. Immediate remediation involves restricting internal index access.

Technical Analysis

The vulnerability resides within how the Splunk MCP Server app logs information. It improperly handles sensitive data when writing to the internal Splunk index (_internal), specifically failing to sanitize session and authorization tokens.

An authenticated attacker with sufficient privileges—specifically those holding roles with access to the _internal index—can query this index to retrieve these tokens. This bypasses security controls intended to protect session integrity.

Affected Versions

Splunk MCP Server app versions 1.0 before 1.0.3.

Exploitation Flow

Successful exploitation requires a multi-step process:

1. Access Acquisition: An attacker must already possess an authenticated account on the Splunk instance.
2. Privilege/Index Access: The account must have permissions to search the _internal index or hold the mcp_tool_admin capability.
3. Log Retrieval: The attacker executes a search query against the _internal index to filter for logs generated by the MCP Server component.
4. Data Extraction: Sensitive tokens are identified within the log output and extracted for unauthorized impersonation.

Forensic Investigation

When investigating potential exploitation of this vulnerability, focus on the following forensic artifacts:

1. Search Auditing: Review Splunk audit logs (_audit index) for search queries performed by high-privilege users against the _internal index.
2. Component Logs: Examine the specific logs generated by the MCP Server app for indicators of excessive token exposure.
3. Capability Monitoring: Audit user role assignments to identify accounts with unauthorized mcp_tool_admin capabilities or excessive access to internal indexes.

Detection

To detect potential exploitation attempts, implement the following query in your environment:

index=_internal sourcetype=splunk_mcp_server "session_token" OR "auth_token"

Mitigation

Role Review

Audit all user roles and capabilities. Remove mcp_tool_admin from non-administrative users.

Index Restriction

Strictly limit access to the _internal index to authorized administrator roles only.

Update

Upgrade Splunk MCP Server app to version 1.0.3 or higher immediately.

Sources

• MITRE CVE-2026-20205
• Splunk Advisory SVD-2026-0407