{"id":"CVE-2026-63119","state":"PUBLISHED","title":"MCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)","description":"MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StdioTransport and MCP::Client::Stdio in the mcp gem use IO#gets without a byte limit, allowing a peer that sends data without a newline to exhaust process memory. This issue is fixed in version 0.23.0.","publishedAt":"2026-07-29T19:12:07.687Z","updatedAt":"2026-07-29T19:28:41.352Z","severity":{"score":6.2,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["modelcontextprotocol ruby-sdk"],"affected":[{"vendor":"modelcontextprotocol","product":"ruby-sdk","versions":[{"version":"< 0.23.0","status":"affected"}]}],"references":["https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-7683-3w9x-ch42","https://github.com/modelcontextprotocol/ruby-sdk/commit/267b8fa6285453525c81ce43db6b7dcd7a8a8c2f","https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0"],"weaknesses":["CWE-400","CWE-770"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/63xxx/CVE-2026-63119.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63119","state":"PUBLISHED","datePublished":"2026-07-29T19:12:07.687Z","dateUpdated":"2026-07-29T19:28:41.352Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-07-15T16:54:55.816Z"},"containers":{"cna":{"title":"MCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)","descriptions":[{"lang":"en","value":"MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StdioTransport and MCP::Client::Stdio in the mcp gem use IO#gets without a byte limit, allowing a peer that sends data without a newline to exhaust process memory. This issue is fixed in version 0.23.0."}],"affected":[{"vendor":"modelcontextprotocol","product":"ruby-sdk","versions":[{"version":"< 0.23.0","status":"affected"}]}],"references":[{"url":"https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-7683-3w9x-ch42","name":"https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-7683-3w9x-ch42","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/modelcontextprotocol/ruby-sdk/commit/267b8fa6285453525c81ce43db6b7dcd7a8a8c2f","name":"https://github.com/modelcontextprotocol/ruby-sdk/commit/267b8fa6285453525c81ce43db6b7dcd7a8a8c2f","tags":["x_refsource_MISC"]},{"url":"https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0","name":"https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":6.2,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-400","lang":"en","description":"CWE-400: Uncontrolled Resource Consumption","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-770","lang":"en","description":"CWE-770: Allocation of Resources Without Limits or Throttling","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-07-29T19:12:07.687Z"},"source":{"advisory":"GHSA-7683-3w9x-ch42","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-7683-3w9x-ch42","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-29T19:28:33.562204Z","id":"CVE-2026-63119","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-07-29T19:28:41.352Z"}}]}}}