CVE-2026-76404: Critical Remote Code Execution Hits Splunk MCP Server App (CVSS 9.1)
Do Son 
TL;DR
Splunk fixed 17 vulnerabilities across its apps and add-ons on August 19, 2026. The worst, CVE-2026-76404, is a critical remote code execution flaw in the MCP Server app. It scores 9.1. Splunk reports no confirmed exploitation in the wild.
- Total: 17 CVEs
- Severity: 1 Critical · 9 High · 7 Medium
- Actively exploited: None confirmed
- Highest severity: 9.1 (Critical · CVSSv3) — CVE-2026-76404
- Action: Apply the latest security updates now
Notable CVEs
| CVE | CVSS (CVSSv3) | Type | Fixed in | Status |
|---|---|---|---|---|
| CVE-2026-76404 | 9.1 | CWE-502 | 1.2.1 | Not exploited |
| CVE-2026-76389 | 8.8 | CWE-918 | 1.0.3 | Not exploited |
| CVE-2026-76395 | 8.8 | CWE-502 | 6.0.0 | Not exploited |
| CVE-2026-76391 | 8.3 | CWE-863 | 6.0.0 | Not exploited |
| CVE-2026-76394 | 8.3 | CWE-862 | 6.0.0 | Not exploited |
| CVE-2026-76402 | 8.2 | CWE-918 | 2.2.7 | Not exploited |
| CVE-2026-76397 | 8.1 | CWE-639 | 6.0.0 | Not exploited |
| CVE-2026-76399 | 8.1 | CWE-732 | 6.0.1 | Not exploited |
Why It Matters
Splunk apps extend a platform that sits at the heart of many SOCs. A flaw in those add-ons can therefore reach sensitive data. This remote code execution bug lets an attacker run commands on the host.
Five apps received fixes in one release. The affected set includes the AI Toolkit, Connect for Kafka, and the Cisco Talos add-on. Because Splunk handles credentials and logs, the stakes stay high.
How the Attack Works
The lead flaw lives in the MCP Server app’s credential management component. That component deserializes stored data without checking its type. As a result, crafted data can trigger remote code execution.
A user with the Splunk admin role can abuse this path. The bug maps to CWE-502, unsafe deserialization of untrusted data. Splunk lists every fix in its apps and add-ons hardening advisory.
Other Notable Flaws
CVE-2026-76395 is a second deserialization RCE, this time in the AI Toolkit, scoring 8.8. CVE-2026-76389 is an SSRF flaw in the Cisco Talos add-on, also at 8.8. Several access control and SSRF bugs round out the list.
Affected Versions
The MCP Server app is vulnerable below 1.2.1. The AI Toolkit is affected below 6.0.1 and 6.0.0. Other fixes cover Connect for Kafka, the Talos add-on, and On-Call. Splunk does not publish install-count estimates.
Patch and Mitigation Steps
Upgrade each affected app to its fixed version. Move the MCP Server app to 1.2.1 and the AI Toolkit to 6.0.1. As a stopgap, turn off or remove the vulnerable apps. Review the advisory for per-app fixed versions.
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