{"cve":"CVE-2026-67431","nvd":{"published":"2026-07-29T20:17:12.120","modified":"2026-10-24T13:10:00.147","status":"Deferred","description":"MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem does not bind a session ID to a session owner, allowing an attacker with a stolen session ID to send tools/call requests that execute in the victim's session. This issue is fixed in version 0.23.0.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N","score":8.3},"cvss_v3":null,"cwes":["CWE-284"],"references":["https://github.com/modelcontextprotocol/ruby-sdk/commit/35466605319a34e4c7808712ae9bb1ca1afb2356","https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0","https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-5p9g-j988-pcwv","https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-5p9g-j988-pcwv"],"products":[],"source":"nvd","synced_at":"2026-10-24T16:53:27.712498749+00:00"},"epss":{"cve":"CVE-2026-67431","score":0.00363,"percentile":0.29895,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-5p9g-j988-pcwv","url":"https://osv.dev/vulnerability/GHSA-5p9g-j988-pcwv","summary":"MCP Ruby SDK: Ruby SSE Session Poisoning","modified":"2026-07-30T15:00:31.159150886Z","packages":[{"ecosystem":"RubyGems","name":"mcp","purl":"pkg:gem/mcp","ranges":["<0.23.0"],"fixed":["0.23.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}