CVE-2026-67431
MCP Ruby SDK: Ruby SSE Session Poisoning
- State
- Published
- Severity
- 8.3 High
- Published
- Jul 29, 2026
- Updated
- Jul 30, 2026
- Reserved
- Jul 29, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.3 High | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N | GitHub_M |
Weaknesses
- CWE-284 Improper Access Control
Affected Products
| Product | Versions |
|---|---|
ruby-sdkmodelcontextprotocol |
|
References
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