CVE-2026-63119CWE-400CWE-770denial-of-service

CVE-2026-63119

Medium · published July 30, 2026

CVSS v3.1
6.2
EPSS
0%
Percentile
7.5
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::StdioTransport and MCP::Client::Stdio in the mcp gem use IO#gets without a byte limit, allowing a peer that sends data without a newline to exhaust process memory. This issue is fixed in version 0.23.0.

The record
Technical detail
CVSS v3.1
6.2 · MEDIUM
Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS v4.0
Not supplied
EPSS
0.00184 · 7.5th percentile
Weaknesses
CWE-400 · Uncontrolled Resource Consumption; CWE-770 · Allocation of Resources Without Limits or Throttling
Published
2026-07-30T00:17Z
References (4)
https://github.com/modelcontextprotocol/ruby-sdk/commit/267b8fa6285453525c81ce43db6b7dcd7a8a8c2f · [email protected]https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0 · [email protected]https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-7683-3w9x-ch42 · [email protected]https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-7683-3w9x-ch42 · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 29 JUL 19:12Z
    MCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)
    cvelistv5