Bug 2376485 (CVE-2025-53366)

Summary: CVE-2025-53366 mcp: MCP SDK Denial of Service Vulnerability
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: anpicker, bparees, david.sastre, hasun, jfula, jowilson, nyancey, ometelka, ptisnovs, syedriko, xdharmai
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in MCP. The MCP Python SDK contains a validation error that leads to an unhandled exception when processing malformed requests. This flaw allows a remote attacker to trigger this condition by sending a crafted request, resulting in an application-level service interruption.
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Description OSIDB Bzimport 2025-07-04 23:01:19 UTC
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.