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 does not bind a session ID to a session owner, allowing an attacker with a stolen session ID to send tools/call requests that execute in the victim's session. This issue is fixed in version 0.23.0.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
Present
Additional conditions required
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
High
Complete data modification
Availability
Low
Partial disruption
CVSS Vector v4.0
Weakness Type (CWE)
References 3
https://github.com/modelcontextprotocol/ruby-sdk/commit/35466605319a34e4c780871…
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-5p9g-…
security-advisories@github.com