CVE-2026-67431

MCP Ruby SDK: Ruby SSE Session Poisoning

Published: Jul 29, 2026Updated: Jul 30, 2026 Sources: CVE List NVDCWE-284

N/ACVSS

NVD MITRE

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.

No summary for this CVE yet.

Weaknesses

CWE-284

Affected Products

modelcontextprotocol

oss-projectaka model context protocol, mcp

ruby-sdkMixed

AI / ML / ai-agent-tooling

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

References

https://github.com/modelcontextprotocol/ruby-sdk/commit/35466605319a34e4c7808712ae9bb1ca1afb2356

github.com

https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0

github.com

https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-5p9g-j988-pcwv

github.com

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