{"id":"CVE-2026-63119","summary":"MCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)","details":"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.","aliases":["GHSA-7683-3w9x-ch42"],"modified":"2026-07-31T03:49:06.312401188Z","published":"2026-07-29T19:12:07.687Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-400","CWE-770"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63119.json"},"references":[{"type":"WEB","url":"https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63119.json"},{"type":"ADVISORY","url":"https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-7683-3w9x-ch42"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63119"},{"type":"FIX","url":"https://github.com/modelcontextprotocol/ruby-sdk/commit/267b8fa6285453525c81ce43db6b7dcd7a8a8c2f"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/modelcontextprotocol/ruby-sdk","events":[{"introduced":"0"},{"fixed":"267b8fa6285453525c81ce43db6b7dcd7a8a8c2f"},{"fixed":"95feef2dcfba25d92a8963d14b7a3b279122f36f"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"0.23.0"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["v0.22.0","v0.21.0","v0.20.0","v0.19.0","v0.18.0","v0.17.0","v0.16.0","v0.15.0","v0.14.0","v0.13.0","v0.12.0","v0.11.0","v0.10.0","v0.9.2","v0.9.1","v0.8.0","v0.9.0","v0.7.1","v0.7.0","v0.6.0","v0.5.0","v0.4.0","v0.3.0","v0.2.0","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63119.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}