CVE-2026-67432CWE-770

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

High · published July 29, 2026

CVSS v3.1
7.5
EPSS
1%
Percentile
55.6
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS v4.0
Not supplied
EPSS
0.00784 · 55.6th percentile
Weakness
CWE-770 · Allocation of Resources Without Limits or Throttling
Published
2026-07-29T19:17Z
EPSS history
Timeline
  • 29 JUL 19:17Z
    MCP Ruby SDK: Unbounded JSON-RPC request body causes uncontrolled memory allocation in StreamableHTTPTransport
    cvelistv5