CVE-2026-67432
HIGHMCP Ruby SDK: Unbounded JSON-RPC request body causes uncontrolled memory allocation in StreamableHTTPTransport
Title source: cnaDescription
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.
References (3)
Core 3
Core References
X_Refsource_Confirm x_refsource_confirm
https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-h669-8m4g-r2hc
X_Refsource_Misc x_refsource_misc
https://github.com/modelcontextprotocol/ruby-sdk/commit/772e0cb1f9db69312006926eee59a7287ad50166
X_Refsource_Misc x_refsource_misc
https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0
Scores
CVSS v3
7.5
EPSS
0.0044
EPSS Percentile
35.9%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
yes
Technical Impact
partial
Details
CWE
CWE-770
Status
published
Products (2)
modelcontextprotocol/ruby-sdk
< 0.23.0
rubygems/mcp
0 - 0.23.0RubyGems
Published
Jul 29, 2026
Tracked Since
Jul 30, 2026