Is there a public exploit for CVE-2025-53366?

No public exploit for CVE-2025-53366 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2025-53366?

CVE-2025-53366 scores CVSS 8.7 (v4.0), rated high. EPSS puts the chance of exploitation in the next 30 days at 9.75%.

What does CVE-2025-53366 affect?

CVE-2025-53366 affects modelcontextprotocol mcp. It is part of the AI and agent stack (Model Context Protocol).

8.7 High

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP).

CVE-2025-53366

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to version 1.9.4, a validation error in the MCP SDK can cause an unhandled exception when processing malformed requests, resulting in service unavailability (500 errors) until manually restarted. Impact may vary depending on the deployment conditions, and presence of infrastructure-level resilience measures. Version 1.9.4 contains a patch for the issue.

Part of the AI stack

This affects Model Context Protocol, in MCP & tool servers.

Assessment

CVSS: 8.7 (v4.0)
Severity: High
EPSS: 9.75% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 4 July 2025
Last updated: 16 July 2026
Affected: modelcontextprotocol · python-sdk · mcp
Weakness: CWE-248
Assigner: security-advisories@github.com

CVSS vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

At the source

References

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