CVE-2026-67431

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Source

https://cve.org/CVERecord?id=CVE-2026-67431

Import Source

https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-67431.json

JSON Data

https://api.osv.dev/v1/vulns/CVE-2026-67431

Aliases

GHSA-5p9g-j988-pcwv

Published

2026-07-29T19:15:32.340Z

Modified

2026-07-30T04:03:36.912523596Z

Severity

8.3 (High) CVSS_V4 - 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 CVSS Calculator

Summary

MCP Ruby SDK: Ruby SSE Session Poisoning

Details

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.

Database specific

{
    "cna_assigner": "GitHub_M",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/67xxx/CVE-2026-67431.json",
    "cwe_ids": [
        "CWE-284"
    ]
}

References

Affected packages

Git / github.com/modelcontextprotocol/ruby-sdk

Affected ranges

Type

GIT

Repo

https://github.com/modelcontextprotocol/ruby-sdk

Events

Introduced

Fixed

95feef2dcfba25d92a8963d14b7a3b279122f36f

Database specific

{
    "extracted_events": [
        {
            "introduced": "0"
        },
        {
            "fixed": "0.23.0"
        }
    ],
    "source": "AFFECTED_FIELD"
}

Affected versions

v0.*

v0.1.0

v0.10.0

v0.11.0

v0.12.0

v0.13.0

v0.14.0

v0.15.0

v0.16.0

v0.17.0

v0.18.0

v0.19.0

v0.2.0

v0.20.0

v0.21.0

v0.22.0

v0.3.0

v0.4.0

v0.5.0

v0.6.0

v0.7.0

v0.7.1

v0.8.0

v0.9.0

v0.9.1

v0.9.2

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-67431.json"