CVE-2026-67432

MCP Ruby SDK: Unbounded JSON-RPC request body causes uncontrolled memory allocation in StreamableHTTPTransport

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 reads and parses an entire JSON-RPC POST body without a size limit, allowing an unauthenticated remote attacker to exhaust process memory. This issue is fixed in version 0.23.0.

Affected

modelcontextprotocol · ruby-sdk

CVSS v3.1 GITHUB

7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

0.78% chance of exploitation in the next 30 days, 55th percentile

Published

2026-07-29

Proof-of-concept exploits (1)

• advisories/GHSA-h669-8m4g-r2hc

References

• CVE Record
• NVD entry