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

Quick assessment

Affected
modelcontextprotocol ruby-sdk
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

MCP Ruby SDK是Model Context Protocol开源的一个用于构建和交互模型上下文协议客户端的Ruby软件开发工具包。 MCP Ruby SDK 0.9.2之前版本存在安全漏洞，该漏洞源于streamable_http_transport.rb实现存在会话劫持问题，可能导致攻击者完全劫持受害者的服务器发送事件流并拦截所有实时数据。

AI Predicted 7.5 Difficulty: Moderate EPSS 0.54% · P43

Possible ATT&CK Techniques 2 AI

T1076 T1557 · Adversary-in-the-Middle
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I. Basic Information for CVE-2026-33946

Vulnerability Information
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Vulnerability Title
MCP Ruby SDK: Insufficient Session Binding Allows SSE Stream Hijacking via Session ID Replay
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
会话固定
Source: CVE Program / CVE List V5
Vulnerability Title
MCP Ruby SDK 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
MCP Ruby SDK是Model Context Protocol开源的一个用于构建和交互模型上下文协议客户端的Ruby软件开发工具包。 MCP Ruby SDK 0.9.2之前版本存在安全漏洞，该漏洞源于streamable_http_transport.rb实现存在会话劫持问题，可能导致攻击者完全劫持受害者的服务器发送事件流并拦截所有实时数据。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
modelcontextprotocol ruby-sdk < 0.9.2 -

II. Public POCs for CVE-2026-33946

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III. Intelligence Information for CVE-2026-33946

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Patches & Fixes for CVE-2026-33946 (2)

Vendor Advisories for CVE-2026-33946 (1)

Vendor Pages for CVE-2026-33946 (1)

Other References for CVE-2026-33946 (1)

IV. Related Vulnerabilities

Same product: ruby-sdk
Same vendor: modelcontextprotocol
Same weakness: CWE-384

V. Comments for CVE-2026-33946

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