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MCP Python SDK has Unhandled Exception in Streamable HTTP Transport, Leading to Denial of Service

as of Jul 4, 2025 · applies to mcp < 1.10.0 · canonical · codexguild.com/kb/ghsa-j975-95f5-7wqh · exported 2026-10-11

Canonical as of Jul 4, 2025

MCP Python SDK has Unhandled Exception in Streamable HTTP Transport, Leading to Denial of Service

High severity. Affects mcp < 1.10.0. Upgrade to 1.10.0 or later.

CVE-2025-53365 / GHSA-j975-95f5-7wqh · severity: high · PyPI

Affected

mcp < 1.10.0 → fixed in 1.10.0

Details

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.

Source: GHSA-j975-95f5-7wqh — GitHub Advisory Database (CC-BY-4.0).