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CVE-2026-33946

MEDIUM

5.9

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.

CVE Details

CVSS v3.1 Score5.9

SeverityMEDIUM

CVSS VectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack VectorNETWORK

ComplexityHIGH

Privileges RequiredNONE

User InteractionNONE

Published3/27/2026

Last Modified4/2/2026

Sourcenvd

Honeypot Sightings0

Affected Products

lfprojects:mcp_ruby_sdk

Weaknesses (CWE)

CWE-384CWE-639CWE-384

References

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

https://github.com/modelcontextprotocol/go-sdk/blob/main/mcp/streamable.go#L281C1-L288C2(security-advisories@github.com)

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

https://github.com/modelcontextprotocol/ruby-sdk/blob/main/examples/streamable_http_server.rb(security-advisories@github.com)

https://github.com/modelcontextprotocol/ruby-sdk/commit/db40143402d65b4fb6923cec42d2d72cb89b3874(security-advisories@github.com)

https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.9.2(security-advisories@github.com)

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

https://hackerone.com/reports/3556146(security-advisories@github.com)

https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-qvqr-5cv7-wh35(134c704f-9b21-4f2e-91b3-4a467353bcc0)

IOC Correlations

No correlations recorded

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