MCP Inspector - Authentication Bypass (CVE-2025-49596)
Description
The MCP inspector is a developer tool for testing and debugging MCP servers. Versions of MCP Inspector below 0.14.1 are vulnerable to remote code execution due to lack of authentication between the Inspector client and proxy, allowing unauthenticated requests to launch MCP commands over stdio. Users should immediately upgrade to version 0.14.1 or later to address these vulnerabilities.
psychologyCrowdSec Analysis
CVE-2025-49596 is a critical vulnerability in MCP Inspector versions prior to 0.14.1 that allows unauthenticated remote code execution due to missing authentication between the Inspector client and proxy. Attackers can exploit this flaw to send unauthorized requests and execute arbitrary MCP commands, potentially leading to full system compromise. Immediate upgrades to version 0.14.1 or later are strongly recommended to mitigate this severe risk.
CrowdSec has been tracking this vulnerability and its exploits since 24th of September 2025.
CrowdSec has not observed any significant exploitation activity targeting CVE-2025-49596 across its network. As a result, no community-driven trend analysis is available for this vulnerability at this time.
Attackers exploit unauthenticated access to the /sse endpoint with parameters like transportType=stdio and command=echo to remotely execute arbitrary MCP commands on vulnerable MCP Inspector instances. These requests do not require authentication and can be used to gain code execution on affected servers.
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| Event | Date |
|---|---|
| CVE Published | 2025-06-13 |
| Rule Released | 2025-09-24 |
| CrowdSec First Seen | 2025-10-15 |
Remediation & Protection
External References
- https://github.com/modelcontextprotocol/inspector/security/advisories/GHSA-7f8r-222p-6f5g
- https://www.oligo.security/blog/critical-rce-vulnerability-in-anthropic-mcp-inspector-cve-2025-49596
- https://thenewstack.io/mcp-vulnerability-exposes-the-ai-untrusted-code-crisis
- https://github.com/modelcontextprotocol/inspector/commit/50df0e1ec488f3983740b4d28d2a968f12eb8979
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2025/CVE-2025-49596.yaml