High 7.5Published Jul 29, 2026

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

Updated under an hour ago (Oct 28, 2026, 2:10 AM ET)

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It affects modelcontextprotocol ruby-sdk. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for modelcontextprotocol ruby-sdk

Exploited in the last 30 days

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.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-770
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Jul 29, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

modelcontextprotocol ruby-sdk modelcontextprotocol:ruby_sdk (from the name)	before 0.23.0	CNA record

References

References

https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-h669-8m4g-r2hc	x-refsource-confirm
https://github.com/modelcontextprotocol/ruby-sdk/commit/772e0cb1f9db69312006926eee59a7287ad50166	x-refsource-misc
https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0	x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.