CVE-2025-53365highDenial of service2025-07-04
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.
What it is
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.
How to check
- Affected: mcp (pip) < 1.10.0.
- Compare your installed version with the range above (command below).
How to fix
- Upgrade mcp to 1.10.0 or later.
pip show mcp | grep VersionSources
More advisories for this tool
- criticalCVE-2026-96620: Claude Agent SDK (Python) resume option lets attackers run commands
- criticalCVE-2026-95182: DeepSeek Harness can be tricked into running a planted fake npx
- criticalLangflow: adding an MCP server runs any command on the host (CVE-2026-105697, CVE-2026-105740)
- criticalCVE-2026-32871: FastMCP OpenAPI Provider has an SSRF & Path Traversal Vulnerability