{"cve":"CVE-2026-33946","nvd":{"published":"2026-03-27T22:16:21.580","modified":"2026-10-26T21:10:00.170","status":"Analyzed","description":"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.","cvss_v4":{"vector":"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","score":8.2},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N","score":5.9},"cwes":["CWE-384","CWE-639"],"references":["https://github.com/modelcontextprotocol/csharp-sdk/blob/main/src/ModelContextProtocol.AspNetCore/SseHandler.cs#L93-L97","https://github.com/modelcontextprotocol/go-sdk/blob/main/mcp/streamable.go#L281C1-L288C2","https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/streamable_http.py#L680-L685","https://github.com/modelcontextprotocol/ruby-sdk/blob/main/examples/streamable_http_server.rb","https://github.com/modelcontextprotocol/ruby-sdk/commit/db40143402d65b4fb6923cec42d2d72cb89b3874"],"products":["lfprojects:mcp_ruby_sdk"],"source":"nvd","synced_at":"2026-10-26T21:38:48.864438205+00:00"},"epss":{"cve":"CVE-2026-33946","score":0.00474,"percentile":0.40687,"date":"2026-10-26"},"kev":null,"osv":[{"id":"GHSA-qvqr-5cv7-wh35","url":"https://osv.dev/vulnerability/GHSA-qvqr-5cv7-wh35","summary":"MCP Ruby SDK: Insufficient Session Binding Allows SSE Stream Hijacking via Session ID Replay","modified":"2026-03-30T20:19:48.069207Z","packages":[{"ecosystem":"RubyGems","name":"mcp","purl":"pkg:gem/mcp","ranges":["<0.9.2"],"fixed":["0.9.2"]}]}],"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."]}