CVE-2025-53365: MCP Python SDK has Unhandled Exception in Streamable HTTP Transport ,Leading to Denial of Service
If a client deliberately triggers an exception after establishing a streamable HTTP session, this can lead to an uncaught ClosedResourceError on the server side, causing the server to crash and requiring a restart to restore service. Impact may vary depending on the deployment conditions, and presence of infrastructure-level resilience measures.
Thank you to Rich Harang for reporting this issue.
Other sources
The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to version 1.10.0, if a client deliberately triggers an exception after establishing a streamable HTTP session, this can lead to an uncaught ClosedResourceError on the server side, causing the server to crash and requiring a restart to restore service. Impact may vary depending on the deployment conditions, and presence of infrastructure-level resilience measures. Version 1.10.0 contains a patch for the issue.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2025-53365?
CVE-2025-53365 has a severity that could lead to service disruption due to server crashes.
How do I fix CVE-2025-53365?
To mitigate CVE-2025-53365, upgrade to version 1.10.0 or later of the MCP Python SDK.
What software is affected by CVE-2025-53365?
CVE-2025-53365 affects the MCP Python SDK versions prior to 1.10.0.
What kind of issue does CVE-2025-53365 cause?
CVE-2025-53365 can cause uncaught ClosedResourceError exceptions, leading to server crashes.
Who is impacted by CVE-2025-53365?
Users of the MCP Python SDK who have not upgraded past version 1.10.0 are impacted by CVE-2025-53365.