CVE-2026-33946

5.9 MEDIUM
Published: March 27, 2026 Modified: April 02, 2026
View on NVD

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.

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
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

Patch Vendor Advisory Exploit Third Party Advisory
https://github.com/modelcontextprotocol/csharp-sdk/blob/main/src/ModelContextProtocol.AspNetCore/SseHandler.cs#L93-L97
Source: security-advisories@github.com
Patch
https://github.com/modelcontextprotocol/go-sdk/blob/main/mcp/streamable.go#L281C1-L288C2
Source: security-advisories@github.com
Patch
https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/streamable_http.py#L680-L685
Source: security-advisories@github.com
Patch
https://github.com/modelcontextprotocol/ruby-sdk/blob/main/examples/streamable_http_server.rb
Source: security-advisories@github.com
Patch
https://github.com/modelcontextprotocol/ruby-sdk/commit/db40143402d65b4fb6923cec42d2d72cb89b3874
Source: security-advisories@github.com
Patch
https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.9.2
Source: security-advisories@github.com
Product Release Notes
https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-qvqr-5cv7-wh35
Source: security-advisories@github.com
Exploit Vendor Advisory
https://hackerone.com/reports/3556146
Source: security-advisories@github.com
Permissions Required
https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-qvqr-5cv7-wh35
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Exploit Vendor Advisory

9 reference(s) from NVD

Quick Stats

CVSS v3 Score
5.9 / 10.0
EPSS (Exploit Probability)
0.0%
13th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

CWE-384 CWE-639 CWE-384

Affected Vendors

lfprojects

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