{"id":"CVE-2026-63119","aliases":["GHSA-7683-3w9x-ch42"],"url":"https://o3.security/vulnerability/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.","published":"2026-07-29T19:12:07.687Z","modified":"2026-08-12T03:51:17.635814998Z","cvss":{"score":6.2,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":{"score":0.00127,"percentile":0.02704,"asOf":"2026-09-12"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"RubyGems","name":"mcp","fixedVersion":"0.23.0"}],"fix":{"url":"https://github.com/modelcontextprotocol/ruby-sdk/commit/267b8fa6285453525c81ce43db6b7dcd7a8a8c2f","label":"modelcontextprotocol/ruby-sdk@267b8fa"},"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:17.635814998Z"}}