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Cleartext Session and Authorization Token Logging in Splunk MCP Server
CVE-2026-20205 is an information-disclosure vulnerability in Splunk MCP Server app versions earlier than 1.0.3. The application records user session and authorization tokens in clear text in internal logging data. A user authorized to access Splunk's internal index, or one granted the high-privilege mcp_tool_admin capability, can read the exposed tokens. Local access to the relevant log files also permits retrieval of the cleartext token data.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
An attacker who obtains the logged session or authorization tokens can access sensitive authentication material associated with other users. Depending on token validity and the authorization model of the consuming services, disclosed tokens may enable unauthorized authenticated access or session impersonation.
If you can’t patch tonight, do this now.
Until the application is upgraded, restrict access to local Splunk log files and to the internal index. Remove unnecessary mcp_tool_admin capability assignments and apply least privilege to roles that can search or view internal logging data. Review potentially exposed tokens and revoke or rotate them where supported.
Patch, then assume compromise.
Upgrade Splunk MCP Server to version 1.0.3 or later, which includes the fix for CVE-2026-20205. Review Splunk roles and capabilities and ensure access to internal indexes is limited to administrator-level roles.
No public exploits tracked yet. Mallory keeps watching.
5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.