{"id":"CVE-2026-33946","summary":"MCP Ruby SDK: Insufficient Session Binding Allows SSE Stream Hijacking via Session ID Replay","details":"MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to version 0.9.2, the Ruby SDK's streamable_http_transport.rb implementation contains a session hijacking vulnerability. An attacker who obtains a valid session ID can completely hijack the victim's Server-Sent Events (SSE) stream and intercept all real-time data. Version 0.9.2 contains a patch.","aliases":["GHSA-qvqr-5cv7-wh35"],"modified":"2026-04-02T13:29:10.610602Z","published":"2026-03-27T21:20:07.900Z","database_specific":{"cwe_ids":["CWE-384","CWE-639"],"cna_assigner":"GitHub_M","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33946.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33946.json"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/csharp-sdk/blob/main/src/ModelContextProtocol.AspNetCore/SseHandler.cs#L93-L97"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/go-sdk/blob/main/mcp/streamable.go#L281C1-L288C2"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/streamable_http.py#L680-L685"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/ruby-sdk/blob/main/examples/streamable_http_server.rb"},{"type":"FIX","url":"https://github.com/modelcontextprotocol/ruby-sdk/commit/db40143402d65b4fb6923cec42d2d72cb89b3874"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.9.2"},{"type":"ADVISORY","url":"https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-qvqr-5cv7-wh35"},{"type":"WEB","url":"https://hackerone.com/reports/3556146"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33946"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/modelcontextprotocol/ruby-sdk","events":[{"introduced":"0"},{"fixed":"3fc7bcd2683d2200d42f79ab46752dc65f896db1"}],"database_specific":{"versions":[{"introduced":"0"},{"fixed":"0.9.2"}]}}],"versions":["v0.1.0","v0.2.0","v0.3.0","v0.4.0","v0.5.0","v0.6.0","v0.7.0","v0.7.1","v0.8.0","v0.9.0","v0.9.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33946.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:H/VI:N/VA:N/SC:N/SI:N/SA:N"}]}