CVE-2026-33946 MCP Ruby SDK: Insufficient Session Binding Allows SSE Stream Hijacking via Session ID Replay

🗓️ 27 Mar 2026 21:20:07Reported by GitHub_MType

MCP Ruby SDK before 0.9.2 allows server sent events hijacking via session replay; patch released in 0.9.2.

Reporter	Title	Published	Views	Family All 15
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
EUVD	EUVD-2026-16866	27 Mar 202621:20	–	euvd
Github Security Blog	MCP Ruby SDK: Insufficient Session Binding Allows SSE Stream Hijacking via Session ID Replay	27 Mar 202618:36	–	github
NVD	CVE-2026-33946	27 Mar 202622:16	–	nvd
OSV	CVE-2026-33946 MCP Ruby SDK: Insufficient Session Binding Allows SSE Stream Hijacking via Session ID Replay	27 Mar 202621:20	–	osv
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

[
  {
    "vendor": "modelcontextprotocol",
    "product": "ruby-sdk",
    "versions": [
      {
        "version": "< 0.9.2",
        "status": "affected"
      }
    ]
  }
]

Source	Link
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
github	www.github.com/modelcontextprotocol/ruby-sdk/commit/db40143402d65b4fb6923cec42d2d72cb89b3874
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/ruby-sdk/security/advisories/GHSA-qvqr-5cv7-wh35
github	www.github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/streamable_http.py
hackerone	www.hackerone.com/reports/3556146

27 Mar 2026 21:20Current

CVSS 48.2

EPSS0.00465