{"action":"Upgrade mcp to 0.9.2 or later.","affected":[{"fixed":"0.9.2","introduced":"0"}],"component":"mcp","cve_ids":["CVE-2026-33946"],"ecosystem":"RubyGems","epss":0.00474,"exploited":false,"fixed_versions":["0.9.2"],"ghsa_id":"GHSA-qvqr-5cv7-wh35","id":"tcs_01M5KEN3CR37EZWG7FQF0NXERV","modified_at":"2026-03-30T20:19:48.069207Z","published_at":"2026-03-27T18:36:45Z","references":["https://osv.dev/vulnerability/GHSA-qvqr-5cv7-wh35","https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-qvqr-5cv7-wh35","https://nvd.nist.gov/vuln/detail/CVE-2026-33946","https://github.com/modelcontextprotocol/ruby-sdk/commit/db40143402d65b4fb6923cec42d2d72cb89b3874","https://hackerone.com/reports/3556146","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","https://github.com/modelcontextprotocol/ruby-sdk/blob/main/examples/streamable_http_server.rb","https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.9.2","https://github.com/rubysec/ruby-advisory-db/blob/master/gems/mcp/CVE-2026-33946.yml"],"severity":{"label":"medium","score":5.9},"sources":[{"source":"osv","source_id":"GHSA-qvqr-5cv7-wh35","url":"https://osv.dev/vulnerability/GHSA-qvqr-5cv7-wh35"},{"source":"nvd","source_id":"CVE-2026-33946","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33946"}],"summary":"MCP Ruby SDK: Insufficient Session Binding Allows SSE Stream Hijacking via Session ID Replay"}