{"id":"CVE-2026-67431","summary":"MCP Ruby SDK: Ruby SSE Session Poisoning","details":"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.","aliases":["GHSA-5p9g-j988-pcwv"],"modified":"2026-07-30T04:03:36.912523596Z","published":"2026-07-29T19:15:32.340Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-284"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/67xxx/CVE-2026-67431.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/67xxx/CVE-2026-67431.json"},{"type":"FIX","url":"https://github.com/modelcontextprotocol/ruby-sdk/commit/35466605319a34e4c7808712ae9bb1ca1afb2356"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0"},{"type":"ADVISORY","url":"https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-5p9g-j988-pcwv"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-67431"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/modelcontextprotocol/ruby-sdk","events":[{"introduced":"0"},{"fixed":"95feef2dcfba25d92a8963d14b7a3b279122f36f"}],"database_specific":{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"0"},{"fixed":"0.23.0"}]}}],"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-2026-67431.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"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"}]}