Session Management Flaw in MCP Ruby SDK Affects Memory Management
CVE-2026-67430

5.3MEDIUM

Key Information:

Vendor

Modelcontextprotocol

Status
Ruby-sdk
Vendor
CVE Published:
29 July 2026

What is CVE-2026-67430?

A session management vulnerability exists in the MCP Ruby SDK, specifically in the MCP::Server::Transports::StreamableHTTPTransport component prior to version 0.23.0. This flaw allows unbounded retention of ServerSession objects during repeated initialize requests, which can lead to excessive memory usage and potential denial of service due to exhausted process memory. The issue has been resolved in version 0.23.0 with improvements to session expiration handling.

Affected Version(s)

ruby-sdk < 0.23.0

References

https://github.com/modelcontextprotocol/ruby-sdk/security...
x_refsource_CONFIRM
https://github.com/modelcontextprotocol/ruby-sdk/commit/a...
x_refsource_MISC
https://github.com/modelcontextprotocol/ruby-sdk/releases...
x_refsource_MISC

CVSS V3.1

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.