CVE-2025-53365: MCP Python SDK has Unhandled Exception in Streamable HTTP Transport, Leading to Denial of Service
(updated )
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.
References
- github.com/advisories/GHSA-j975-95f5-7wqh
- github.com/modelcontextprotocol/python-sdk
- github.com/modelcontextprotocol/python-sdk/commit/7b420656de48cfdb90b39eb582e60b6d55c2f891
- github.com/modelcontextprotocol/python-sdk/pull/967
- github.com/modelcontextprotocol/python-sdk/releases/tag/v1.10.0
- github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-j975-95f5-7wqh
- github.com/pypa/advisory-database/tree/main/vulns/mcp/PYSEC-2026-1618.yaml
- nvd.nist.gov/vuln/detail/CVE-2025-53365
- pypi.org/project/mcp
Code Behaviors & Features
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