{"id":"PYSEC-2026-1618","summary":"MCP Python SDK has Unhandled Exception in Streamable HTTP Transport, Leading to Denial of Service","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.\n\nThank you to Rich Harang for reporting this issue.","aliases":["CVE-2025-53365","GHSA-j975-95f5-7wqh"],"modified":"2026-07-07T17:47:04.395676741Z","published":"2026-07-07T16:02:56.105116Z","references":[{"type":"WEB","url":"https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-j975-95f5-7wqh"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-53365"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/python-sdk/pull/967"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/python-sdk/commit/7b420656de48cfdb90b39eb582e60b6d55c2f891"},{"type":"PACKAGE","url":"https://github.com/modelcontextprotocol/python-sdk"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.10.0"},{"type":"PACKAGE","url":"https://pypi.org/project/mcp"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-j975-95f5-7wqh"}],"affected":[{"package":{"name":"mcp","ecosystem":"PyPI","purl":"pkg:pypi/mcp"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.10.0"}]}],"versions":["0.9.1","1.0.0","1.1.0","1.1.1","1.1.2","1.1.3","1.2.0","1.2.0rc1","1.2.1","1.3.0","1.3.0rc1","1.4.0","1.4.1","1.5.0","1.6.0","1.7.0","1.7.1","1.8.0","1.8.1","1.9.0","1.9.1","1.9.2","1.9.3","1.9.4"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/mcp/PYSEC-2026-1618.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"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"}]}