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CVE-2026-33946

Published: Mar 27, 2026

Modified: Mar 30, 2026

PUBLISHED

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.

Vendor	Product	Versions
modelcontextprotocol	ruby-sdk	affected `< 0.9.2`

Weaknesses (CWE)

References

https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-qvqr-5cv7-wh35

x_refsource_CONFIRM

https://github.com/modelcontextprotocol/ruby-sdk/commit/db40143402d65b4fb6923cec42d2d72cb89b3874

x_refsource_MISC

https://hackerone.com/reports/3556146

x_refsource_MISC

https://github.com/modelcontextprotocol/csharp-sdk/blob/main/src/ModelContextProtocol.AspNetCore/SseHandler.cs#L93-L97

x_refsource_MISC

https://github.com/modelcontextprotocol/go-sdk/blob/main/mcp/streamable.go#L281C1-L288C2

x_refsource_MISC

https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/streamable_http.py#L680-L685

x_refsource_MISC

https://github.com/modelcontextprotocol/ruby-sdk/blob/main/examples/streamable_http_server.rb

x_refsource_MISC

https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.9.2

x_refsource_MISC

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