{"items":[{"id":"NVI-00012028","kind":"vulnerability","title":"MCP Python SDK: Unbounded Session Accumulation in StreamableHTTP Transport Enables Resource Exhaustion","revision":2,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-84m7-p3x7-pcfv","CVE-2026-59951"],"plain_summary":"GitHub lists this reviewed advisory for mcp, mcp. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.","review_status":"source_listed","control_topics":[],"public_actions":[{"summary":"Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.","source_ids":["sr-51fcd9651025f2604030959c253376c2"],"action_type":"investigate","limitations":"Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system.","current_supported_target":null}],"schema_version":"1.1.0","source_metrics":[{"kind":"CVSS","as_of":"2026-10-15T20:13:14.000Z","value":"7.5 medium","meaning":"GitHub source severity; exploitability and local consequence require separate evidence.","source_id":"sr-8e14075795fb06ea77a7f36f730d5efb"},{"kind":"EPSS","as_of":"2026-10-31T12:00:27.000Z","value":"0.458%","meaning":"FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.39727. Missing scores are unknown.","source_id":"sr-51fcd9651025f2604030959c253376c2"}],"why_it_matters":"Published affected context helps an owner decide what evidence to gather. This report has not examined your application.","related_sources":[{"id":"sr-8e14075795fb06ea77a7f36f730d5efb","url":"https://github.com/advisories/GHSA-84m7-p3x7-pcfv","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-84m7-p3x7-pcfv","publisher":"GitHub Advisory Database","observed_at":"2026-10-31T23:14:22.124Z"},{"id":"sr-51fcd9651025f2604030959c253376c2","url":"https://www.first.org/epss/data.html","basis":"official_catalog","notes":"FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.","title":"CVE-2026-59951","publisher":"FIRST EPSS","observed_at":"2026-11-01T01:39:43.082Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-8e14075795fb06ea77a7f36f730d5efb"],"technology":"mcp","known_exclusions":[],"conditions_summary":"### Summary\nIn affected versions, a Streamable HTTP server in stateful mode (the default) never reclaimed session state:\n\n- sessions did not expire;\n- a client `DELETE` ended the session but left its entry registered;\n- a session whose first request was refused stayed registered with a running task.\n\nEach session also kept its parsed `initialize` parameters, and the number of sessions was unlimited. A client that could reach the endpoint could grow server memory without bound using ordinary short requests; only a restart reclaimed it.\n\n### Am I affected?\nYes, if you serve MCP over Streamable HTTP in stateful mode and clients you do not fully trust can reach the endpoint. Stateful mode is the default for:\n\n- `FastMCP` (1.x)\n- `MCPServer` and `Server.streamable_http_app()` (2.x)\n- `StreamableHTTPSessionManager`\n\nAffected versions: 1.8.0 through 1.29.1, and 2.0.0 through 2.1.1.\n\nNot affected:\n\n- servers on 1.12.0 or later passing `stateless_http=True` (no sessions are kept)\n- servers using only the stdio or SSE transports\n\nAuthentication limits who can open sessions, not how many a token holder can open.\n\n### Fix\nUpgrade to `mcp` 1.30.0 (1.x) or 2.2.0 (2.x) or later. In those versions","public_affected_ranges":[">= 1.8.0, < 1.30.0"]},{"certainty":"source_listed","source_ids":["sr-8e14075795fb06ea77a7f36f730d5efb"],"technology":"mcp","known_exclusions":[],"conditions_summary":"### Summary\nIn affected versions, a Streamable HTTP server in stateful mode (the default) never reclaimed session state:\n\n- sessions did not expire;\n- a client `DELETE` ended the session but left its entry registered;\n- a session whose first request was refused stayed registered with a running task.\n\nEach session also kept its parsed `initialize` parameters, and the number of sessions was unlimited. A client that could reach the endpoint could grow server memory without bound using ordinary short requests; only a restart reclaimed it.\n\n### Am I affected?\nYes, if you serve MCP over Streamable HTTP in stateful mode and clients you do not fully trust can reach the endpoint. Stateful mode is the default for:\n\n- `FastMCP` (1.x)\n- `MCPServer` and `Server.streamable_http_app()` (2.x)\n- `StreamableHTTPSessionManager`\n\nAffected versions: 1.8.0 through 1.29.1, and 2.0.0 through 2.1.1.\n\nNot affected:\n\n- servers on 1.12.0 or later passing `stateless_http=True` (no sessions are kept)\n- servers using only the stdio or SSE transports\n\nAuthentication limits who can open sessions, not how many a token holder can open.\n\n### Fix\nUpgrade to `mcp` 1.30.0 (1.x) or 2.2.0 (2.x) or later. In those versions","public_affected_ranges":[">= 2.0.0, < 2.2.0"]}],"null_published_at":"2026-11-01T22:58:19.126Z","source_updated_at":"2026-10-15T20:13:14.000Z","source_disclosed_at":"2026-10-15T20:13:13.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.","null_first_observed_at":"2026-10-31T23:14:22.124Z"},{"id":"NVI-00012028","kind":"vulnerability","title":"MCP Python SDK: Unbounded Session Accumulation in StreamableHTTP Transport Enables Resource Exhaustion","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-84m7-p3x7-pcfv","CVE-2026-59951"],"plain_summary":"GitHub lists this reviewed advisory for mcp, mcp. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.","review_status":"source_listed","control_topics":[],"public_actions":[{"summary":"Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.","source_ids":["sr-8e14075795fb06ea77a7f36f730d5efb"],"action_type":"investigate","limitations":"Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system.","current_supported_target":null}],"schema_version":"1.1.0","source_metrics":[{"kind":"CVSS","as_of":"2026-10-15T20:13:14.000Z","value":"7.5 medium","meaning":"GitHub source severity; exploitability and local consequence require separate evidence.","source_id":"sr-8e14075795fb06ea77a7f36f730d5efb"}],"why_it_matters":"Published affected context helps an owner decide what evidence to gather. This report has not examined your application.","related_sources":[{"id":"sr-8e14075795fb06ea77a7f36f730d5efb","url":"https://github.com/advisories/GHSA-84m7-p3x7-pcfv","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-84m7-p3x7-pcfv","publisher":"GitHub Advisory Database","observed_at":"2026-10-31T23:14:22.124Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-8e14075795fb06ea77a7f36f730d5efb"],"technology":"mcp","known_exclusions":[],"conditions_summary":"### Summary\nIn affected versions, a Streamable HTTP server in stateful mode (the default) never reclaimed session state:\n\n- sessions did not expire;\n- a client `DELETE` ended the session but left its entry registered;\n- a session whose first request was refused stayed registered with a running task.\n\nEach session also kept its parsed `initialize` parameters, and the number of sessions was unlimited. A client that could reach the endpoint could grow server memory without bound using ordinary short requests; only a restart reclaimed it.\n\n### Am I affected?\nYes, if you serve MCP over Streamable HTTP in stateful mode and clients you do not fully trust can reach the endpoint. Stateful mode is the default for:\n\n- `FastMCP` (1.x)\n- `MCPServer` and `Server.streamable_http_app()` (2.x)\n- `StreamableHTTPSessionManager`\n\nAffected versions: 1.8.0 through 1.29.1, and 2.0.0 through 2.1.1.\n\nNot affected:\n\n- servers on 1.12.0 or later passing `stateless_http=True` (no sessions are kept)\n- servers using only the stdio or SSE transports\n\nAuthentication limits who can open sessions, not how many a token holder can open.\n\n### Fix\nUpgrade to `mcp` 1.30.0 (1.x) or 2.2.0 (2.x) or later. In those versions","public_affected_ranges":[">= 1.8.0, < 1.30.0"]},{"certainty":"source_listed","source_ids":["sr-8e14075795fb06ea77a7f36f730d5efb"],"technology":"mcp","known_exclusions":[],"conditions_summary":"### Summary\nIn affected versions, a Streamable HTTP server in stateful mode (the default) never reclaimed session state:\n\n- sessions did not expire;\n- a client `DELETE` ended the session but left its entry registered;\n- a session whose first request was refused stayed registered with a running task.\n\nEach session also kept its parsed `initialize` parameters, and the number of sessions was unlimited. A client that could reach the endpoint could grow server memory without bound using ordinary short requests; only a restart reclaimed it.\n\n### Am I affected?\nYes, if you serve MCP over Streamable HTTP in stateful mode and clients you do not fully trust can reach the endpoint. Stateful mode is the default for:\n\n- `FastMCP` (1.x)\n- `MCPServer` and `Server.streamable_http_app()` (2.x)\n- `StreamableHTTPSessionManager`\n\nAffected versions: 1.8.0 through 1.29.1, and 2.0.0 through 2.1.1.\n\nNot affected:\n\n- servers on 1.12.0 or later passing `stateless_http=True` (no sessions are kept)\n- servers using only the stdio or SSE transports\n\nAuthentication limits who can open sessions, not how many a token holder can open.\n\n### Fix\nUpgrade to `mcp` 1.30.0 (1.x) or 2.2.0 (2.x) or later. In those versions","public_affected_ranges":[">= 2.0.0, < 2.2.0"]}],"null_published_at":"2026-11-01T01:03:56.623Z","source_updated_at":"2026-10-15T20:13:14.000Z","source_disclosed_at":"2026-10-15T20:13:13.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"First indexed by Null; source disclosure date is shown separately.","null_first_observed_at":"2026-10-31T23:14:22.124Z"}],"next_cursor":null,"snapshot_revision":"42594"}