{"items":[{"id":"NVI-00008851","kind":"vulnerability","title":"Model Context Protocol Python SDK: Client fetched server-chosen $ref URLs while validating tool results against output schemas","revision":2,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected.","NVD lastModified does not establish freshness of every associated CPE record."],"lifecycle":"active","identifiers":["GHSA-rwrf-2pqf-9j8j","CVE-2026-116686"],"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-8513e6cf0d3d56ad2c66f7298b532b67"],"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":"2026-10-27T21:05:30.000Z","value":"6.5 medium","meaning":"GitHub source severity; exploitability and local consequence require separate evidence.","source_id":"sr-048041e02d220d92133695febc8dbd69"},{"kind":"CVSS","as_of":"2026-10-28T17:18:03.663Z","value":"6.5 MEDIUM (3.1)","meaning":"security-advisories@github.com severity; no combined Null risk score.","source_id":"sr-8513e6cf0d3d56ad2c66f7298b532b67"}],"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-048041e02d220d92133695febc8dbd69","url":"https://github.com/advisories/GHSA-rwrf-2pqf-9j8j","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-rwrf-2pqf-9j8j","publisher":"GitHub Advisory Database","observed_at":"2026-10-31T21:56:36.327Z"},{"id":"sr-8513e6cf0d3d56ad2c66f7298b532b67","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-116686","basis":"official_catalog","notes":"This product uses data from the NVD API but is not endorsed or certified by the NVD.","title":"CVE-2026-116686","publisher":"NIST National Vulnerability Database","observed_at":"2026-11-03T09:59:08.616Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-048041e02d220d92133695febc8dbd69"],"technology":"mcp","known_exclusions":[],"conditions_summary":"### Summary\nIn affected versions, when a connected MCP server declared an `outputSchema` for a tool, the SDK's client validated each `call_tool` result with `jsonschema`'s default resolver, which fetches any `$ref` it cannot resolve locally by opening the URL. A server could therefore put an `http://`, `https://` or `file://` reference in a tool's output schema and make the client:\n\n- request that URL, or read that local file, from the client's own network position on every call of the tool (the content was used only as a schema and never sent back to the server), and\n- stall: the fetch ran synchronously on the event loop with no timeout, so a target that accepted the connection and then went quiet froze every session in the process for as long as it held the connection.\n\n### Am I affected?\nYes, if your application uses the SDK as an MCP client (`ClientSession` over any transport, `ClientSessionGroup`, or the 2.x `Client`) and calls tools on servers you do not fully control. There was no setting that turned the validation off.\n\nAffected versions: 1.10.0 through 1.29.1, and 2.0.0 through 2.1.1.\n\nNot affected: applications that only build servers. If nothing in your code uses `Client","public_affected_ranges":[">= 2.0.0, < 2.2.0"]},{"certainty":"source_listed","source_ids":["sr-048041e02d220d92133695febc8dbd69"],"technology":"mcp","known_exclusions":[],"conditions_summary":"### Summary\nIn affected versions, when a connected MCP server declared an `outputSchema` for a tool, the SDK's client validated each `call_tool` result with `jsonschema`'s default resolver, which fetches any `$ref` it cannot resolve locally by opening the URL. A server could therefore put an `http://`, `https://` or `file://` reference in a tool's output schema and make the client:\n\n- request that URL, or read that local file, from the client's own network position on every call of the tool (the content was used only as a schema and never sent back to the server), and\n- stall: the fetch ran synchronously on the event loop with no timeout, so a target that accepted the connection and then went quiet froze every session in the process for as long as it held the connection.\n\n### Am I affected?\nYes, if your application uses the SDK as an MCP client (`ClientSession` over any transport, `ClientSessionGroup`, or the 2.x `Client`) and calls tools on servers you do not fully control. There was no setting that turned the validation off.\n\nAffected versions: 1.10.0 through 1.29.1, and 2.0.0 through 2.1.1.\n\nNot affected: applications that only build servers. If nothing in your code uses `Client","public_affected_ranges":[">= 1.10.0, < 1.30.0"]}],"null_published_at":"2026-11-08T15:11:49.385Z","source_updated_at":"2026-10-27T21:05:30.000Z","source_disclosed_at":"2026-10-27T21:05:29.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"Source facts changed; compare the preserved prior revision.","null_first_observed_at":"2026-10-31T21:56:36.327Z"},{"id":"NVI-00008851","kind":"vulnerability","title":"Model Context Protocol Python SDK: Client fetched server-chosen $ref URLs while validating tool results against output schemas","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-rwrf-2pqf-9j8j","CVE-2026-116686"],"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-048041e02d220d92133695febc8dbd69"],"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":"2026-10-27T21:05:30.000Z","value":"6.5 medium","meaning":"GitHub source severity; exploitability and local consequence require separate evidence.","source_id":"sr-048041e02d220d92133695febc8dbd69"}],"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-048041e02d220d92133695febc8dbd69","url":"https://github.com/advisories/GHSA-rwrf-2pqf-9j8j","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-rwrf-2pqf-9j8j","publisher":"GitHub Advisory Database","observed_at":"2026-10-31T21:56:36.327Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-048041e02d220d92133695febc8dbd69"],"technology":"mcp","known_exclusions":[],"conditions_summary":"### Summary\nIn affected versions, when a connected MCP server declared an `outputSchema` for a tool, the SDK's client validated each `call_tool` result with `jsonschema`'s default resolver, which fetches any `$ref` it cannot resolve locally by opening the URL. A server could therefore put an `http://`, `https://` or `file://` reference in a tool's output schema and make the client:\n\n- request that URL, or read that local file, from the client's own network position on every call of the tool (the content was used only as a schema and never sent back to the server), and\n- stall: the fetch ran synchronously on the event loop with no timeout, so a target that accepted the connection and then went quiet froze every session in the process for as long as it held the connection.\n\n### Am I affected?\nYes, if your application uses the SDK as an MCP client (`ClientSession` over any transport, `ClientSessionGroup`, or the 2.x `Client`) and calls tools on servers you do not fully control. There was no setting that turned the validation off.\n\nAffected versions: 1.10.0 through 1.29.1, and 2.0.0 through 2.1.1.\n\nNot affected: applications that only build servers. If nothing in your code uses `Client","public_affected_ranges":[">= 2.0.0, < 2.2.0"]},{"certainty":"source_listed","source_ids":["sr-048041e02d220d92133695febc8dbd69"],"technology":"mcp","known_exclusions":[],"conditions_summary":"### Summary\nIn affected versions, when a connected MCP server declared an `outputSchema` for a tool, the SDK's client validated each `call_tool` result with `jsonschema`'s default resolver, which fetches any `$ref` it cannot resolve locally by opening the URL. A server could therefore put an `http://`, `https://` or `file://` reference in a tool's output schema and make the client:\n\n- request that URL, or read that local file, from the client's own network position on every call of the tool (the content was used only as a schema and never sent back to the server), and\n- stall: the fetch ran synchronously on the event loop with no timeout, so a target that accepted the connection and then went quiet froze every session in the process for as long as it held the connection.\n\n### Am I affected?\nYes, if your application uses the SDK as an MCP client (`ClientSession` over any transport, `ClientSessionGroup`, or the 2.x `Client`) and calls tools on servers you do not fully control. There was no setting that turned the validation off.\n\nAffected versions: 1.10.0 through 1.29.1, and 2.0.0 through 2.1.1.\n\nNot affected: applications that only build servers. If nothing in your code uses `Client","public_affected_ranges":[">= 1.10.0, < 1.30.0"]}],"null_published_at":"2026-10-31T22:13:27.119Z","source_updated_at":"2026-10-27T21:05:30.000Z","source_disclosed_at":"2026-10-27T21:05:29.000Z","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":"2026-10-31T21:56:36.327Z"}],"next_cursor":null,"snapshot_revision":"42594"}