CVE-2026-63119
MEDIUMMCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)
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::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.
References (3)
Core 3
Core References
X_Refsource_Confirm x_refsource_confirm
https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-7683-3w9x-ch42
X_Refsource_Misc x_refsource_misc
https://github.com/modelcontextprotocol/ruby-sdk/commit/267b8fa6285453525c81ce43db6b7dcd7a8a8c2f
X_Refsource_Misc x_refsource_misc
https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0
Scores
CVSS v3
6.2
EPSS
0.0013
EPSS Percentile
3.0%
Attack Vector
LOCAL
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CISA SSVC
Vulnrichment
Exploitation
poc
Automatable
no
Technical Impact
partial
Details
CWE
CWE-400
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