CVE-2026-67431
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.
Published:Jul 29, 2026
Last Modified:Jul 30, 2026
EPS:Jul 29, 2026
EPSS Score:0.00276
CVSS Score:8.3
Affected Products
Vendor
Product
Action
Vendor
Modelcontextprotocol
Product
Ruby-sdk
Modelcontextprotocol
Ruby-sdk
Exploits
No exploit reference
Common Weakness Enumeration
Common Attack Pattern Enumeration and Classification (CAPEC)
Related CVEs
References
Common Vulnerability Scoring System
Attack Vector
Network
Adjacent
Local
Physical
Privileges Required
None
Low
High
User Interaction
None
Required
Scope
Unchanged
Changed
Confidentiality
None
Low
High
Integrity
None
Low
High
Availability
None
Low
High
