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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
Weakness Type (CWE)
References 3
https://github.com/modelcontextprotocol/ruby-sdk/commit/772e0cb1f9db69312006926…
security-advisories@github.com
https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0
security-advisories@github.com
https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-h669-…
security-advisories@github.com