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CVE-2026-33946 Details

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.

Metrics

CVSS 3.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:5.9 MEDIUMVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-qvqr-5cv7-wh35	CISA-ADP	ExploitVendor Advisory
https://github.com/modelcontextprotocol/csharp-sdk/blob/main/src/ModelContextProtocol.AspNetCore/SseHandler.cs#L93-L97	[email protected]	Patch
https://github.com/modelcontextprotocol/go-sdk/blob/main/mcp/streamable.go#L281C1-L288C2	[email protected]	Patch
https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/streamable_http.py#L680-L685	[email protected]	Patch
https://github.com/modelcontextprotocol/ruby-sdk/blob/main/examples/streamable_http_server.rb	[email protected]	Patch
https://github.com/modelcontextprotocol/ruby-sdk/commit/db40143402d65b4fb6923cec42d2d72cb89b3874	[email protected]	Patch
https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.9.2	[email protected]	ProductRelease Notes
https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-qvqr-5cv7-wh35	[email protected]	ExploitVendor Advisory
https://hackerone.com/reports/3556146	[email protected]	Permissions Required

see all 9 references

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-384	Session Fixation	[email protected]
CWE-384	Session Fixation	[email protected]
CWE-639	Authorization Bypass Through User-Controlled Key	[email protected]

Affected Products

Product	Versions
lfprojects mcp ruby sdk	< 0.9.2
CPE cpe:2.3:a:lfprojects:mcp_ruby_sdk:::::::: Remediation No remediation found in references.

Change History

5 change records found show changes

Date	Action	Recorded By
Jun 17, 2026	CVE Modified	[email protected]
Jun 17, 2026	CVE Modified	CISA-ADP
Apr 2, 2026	Initial Analysis	[email protected]
Mar 30, 2026	CVE Modified	CISA-ADP
Mar 27, 2026	New CVE Received	[email protected]