MCP SDKsGHSA-j975-95f5-7wqh
MCP Python SDK has Unhandled Exception in Streamable HTTP Transport, Leading to Denial of Service
HighCVE-2025-53365 · Published Jul 4, 2025 · updated Jul 16, 2026
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.
Affected versions
| Package | Affected | Fixed in |
|---|---|---|
| mcp PyPI | < 1.10.0 | 1.10.0 |
Details and references
- CVSS 4.0
- CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- Severity from
- GitHub (reviewed advisory)
- Weakness
- CWE-248
- Also known as
- CVE-2025-53365, PYSEC-2026-1618
- github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-j975-95f5-7wqh
- nvd.nist.gov/vuln/detail/CVE-2025-53365
- github.com/modelcontextprotocol/python-sdk/pull/967
- github.com/modelcontextprotocol/python-sdk/commit/7b420656de48cfdb90b39eb582e60b6d55c2f891
- github.com/advisories/GHSA-j975-95f5-7wqh
- github.com/modelcontextprotocol/python-sdk
- github.com/modelcontextprotocol/python-sdk/releases/tag/v1.10.0
- github.com/pypa/advisory-database/tree/main/vulns/mcp/PYSEC-2026-1618.yaml
- pypi.org/project/mcp
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