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CVE-2026-67432— MCP Ruby SDK: Unbounded JSON-RPC request body causes uncontrolled memory allocation in StreamableHTTPTransport

CVSS 7.5 · High

Possible ATT&CK Techniques 1AI

T1496 · Resource Hijacking

Affected Version Matrix 1

VendorProductVersion RangeStatus
modelcontextprotocolruby-sdk< 0.23.0affected
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I. Basic Information for CVE-2026-67432

Vulnerability Information
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Vulnerability Title
MCP Ruby SDK: Unbounded JSON-RPC request body causes uncontrolled memory allocation in StreamableHTTPTransport
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5

Affected Products

VendorProductAffected VersionsCPESubscribe
modelcontextprotocolruby-sdk < 0.23.0 -

II. Public POCs for CVE-2026-67432

#POC DescriptionSource LinkShenlong Link
AI-Generated POCPremium
Qwen3.6-35B-A3B · 6925 chars
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III. Intelligence Information for CVE-2026-67432

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Patches & Fixes for CVE-2026-67432 (1)

Vendor Advisories for CVE-2026-67432 (1)

Vendor Pages for CVE-2026-67432 (1)

Same Patch Batch · modelcontextprotocol · 2026-07-29 · 5 CVEs total

CVE-2026-674318.3 HIGHMCP Ruby SDK: Ruby SSE Session Poisoning
CVE-2026-631186.9 MEDIUMMCP Ruby SDK: Streamable HTTP transport lacks DNS-rebinding (Host/Origin) protection
CVE-2026-631196.2 MEDIUMMCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)
CVE-2026-674305.3 MEDIUMMCP Ruby SDK: Unbounded session retention in StreamableHTTPTransport allows memory exhaust

IV. Related Vulnerabilities

Same product: ruby-sdk
Same vendor: modelcontextprotocol
Same weakness: CWE-770

V. Comments for CVE-2026-67432

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