CVE-2026-67430 (Medium) detected in mcp-0.9.0.gem

## CVE-2026-67430 - Medium Severity Vulnerability
Vulnerable Library - mcp-0.9.0.gem

The official Ruby SDK for Model Context Protocol servers and clients

Library home page: https://rubygems.org/gems/mcp-0.9.0.gem

Path to dependency file: /Gemfile.lock

Path to vulnerable library: /vendor/cache/mcp-0.9.0.gem

Dependency Hierarchy:
- manageiq-style-1.6.0.gem (Root Library)
- rubocop-performance-1.26.1.gem
- rubocop-1.85.1.gem
- :x: **mcp-0.9.0.gem** (Vulnerable Library)

Found in base branch: master

Vulnerability Details

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem does not expire sessions by default, so repeated initialize requests retain unbounded ServerSession objects and can exhaust process memory. This issue is fixed in version 0.23.0.

Publish Date: 2026-07-29

URL: CVE-2026-67430

CVSS 3 Score Details (5.3)

Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Network
- Attack Complexity: Low
- Privileges Required: None
- User Interaction: None
- Scope: Unchanged
- Impact Metrics:
- Confidentiality Impact: None
- Integrity Impact: None
- Availability Impact: Low

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: https://github.com/advisories/GHSA-52jp-gj8w-j6xh

Release Date: 2026-07-29

Fix Resolution: mcp - 0.23.0

***
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Start with Gemfile.lock and the vendored mcp-0.9.0.gem, then inspect the dependency declarations that bring mcp in through RuboCop. Upgrade mcp to at least 0.23.0, refresh the lockfile and vendor cache as needed, and run the project's existing checks to confirm the dependency resolves cleanly.

Written by the indexing model from the issue text.