modelcontextprotocol/python-sdk · Security
MCP Python SDK has Unhandled Exception in Streamable HTTP Transport, Leading to Denial of Service
- GHSA ID
- GHSA-j975-95f5-7wqh
- CVE ID
- CVE-2025-53365
- Severity
- high
- Published
- Updated
- CVSS v4
- 8.7 · 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
Description
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.
CWEs
- CWE-248 · Uncaught Exception
References
- https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-j975-95f5-7wqh ↗
- https://github.com/modelcontextprotocol/python-sdk/pull/967 ↗
- https://github.com/modelcontextprotocol/python-sdk/commit/7b420656de48cfdb90b39eb582e60b6d55c2f891 ↗
- https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.10.0 ↗
- https://nvd.nist.gov/vuln/detail/CVE-2025-53365 ↗
- https://github.com/advisories/GHSA-j975-95f5-7wqh ↗
- https://github.com/modelcontextprotocol/python-sdk ↗
- https://github.com/pypa/advisory-database/tree/main/vulns/mcp/PYSEC-2026-1618.yaml ↗
- https://pypi.org/project/mcp ↗