MCP Ruby SDK: Insufficient Session Binding Allows SSE Stream Hijacking via Session ID Replay

🗓️ 27 Mar 2026 18:36:45Reported by GitHub Advisory DatabaseType

Ruby SSE hijack via session identifier replay; lacks binding, ownership checks, and overwrites existing stream.

Reporter	Title	Published	Views	Family All 14
ATTACKERKB	CVE-2026-33946	27 Mar 202621:20	–	attackerkb
Circl	CVE-2026-33946	27 Mar 202603:31	–	circl
CNNVD	MCP Ruby SDK 安全漏洞	27 Mar 202600:00	–	cnnvd
CVE	CVE-2026-33946	27 Mar 202621:20	–	cve
Cvelist	CVE-2026-33946 MCP Ruby SDK: Insufficient Session Binding Allows SSE Stream Hijacking via Session ID Replay	27 Mar 202621:20	–	cvelist
EUVD	EUVD-2026-16866	27 Mar 202621:20	–	euvd
NVD	CVE-2026-33946	27 Mar 202622:16	–	nvd
OSV	GHSA-QVQR-5CV7-WH35 MCP Ruby SDK: Insufficient Session Binding Allows SSE Stream Hijacking via Session ID Replay	27 Mar 202618:36	–	osv
Positive Technologies	PT-2026-28576	27 Mar 202600:00	–	ptsecurity
RedhatCVE	CVE-2026-33946	30 Mar 202617:06	–	redhatcve

Vulners

Node

mcpRange≤0.9.1rubygems

Source	Link
github	www.github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-qvqr-5cv7-wh35
github	www.github.com/modelcontextprotocol/ruby-sdk/commit/db40143402d65b4fb6923cec42d2d72cb89b3874
hackerone	www.hackerone.com/reports/3556146
github	www.github.com/modelcontextprotocol/csharp-sdk/blob/main/src/ModelContextProtocol.AspNetCore/SseHandler.cs
github	www.github.com/modelcontextprotocol/go-sdk/blob/main/mcp/streamable.go
github	www.github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/streamable_http.py
github	www.github.com/modelcontextprotocol/ruby-sdk/blob/main/examples/streamable_http_server.rb
github	www.github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.9.2
nvd	www.nvd.nist.gov/vuln/detail/CVE-2026-33946
github	www.github.com/rubysec/ruby-advisory-db/blob/master/gems/mcp/CVE-2026-33946.yml

30 Mar 2026 20:10Current

5.9Medium risk

Vulners AI Score5.9

CVSS 3.15.9

CVSS 48.2

EPSS0.00465

SSVC