CVE-2026-63119 | BDVDB-2026-353569 Detail

modelcontextprotocolruby-sdk

Description#

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.

Impact#

Per CVSS v3.1: confidentiality impact none, integrity impact none, availability impact high. Attack vector: local.

Weaknesses#

CWE-400 Uncontrolled Resource Consumption
CWE-770 Allocation of Resources Without Limits or Throttling

References#

Exploit#

No public exploit known

History#

Version 12026-07-29Record published in the CVE List.

Published

Published: 2026-07-29
Last modified: 2026-07-29

Vendor information

Vendor: modelcontextprotocol
Product: ruby-sdk

All modelcontextprotocol vulnerabilities

Score

6.2 Medium

EPSS

less than 1%, Very Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 8.5.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Denial of Service

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
< 0.23.0
Fixed
Not stated

Scoring System

CVSS v4.0

Not available

CVSS v3.1

6.2 Medium

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

Metric breakdown
Attack Vector	Local
Attack Complexity	Low
Privileges Required	None
User Interaction	None
Scope	Unchanged
Confidentiality	None
Integrity	None
Availability	High

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).