{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "0.23.0"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "35466605319a34e4c7808712ae9bb1ca1afb2356"
            },
            {
              "fixed": "95feef2dcfba25d92a8963d14b7a3b279122f36f"
            }
          ],
          "repo": "https://github.com/modelcontextprotocol/ruby-sdk",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-5p9g-j988-pcwv"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-284"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/67xxx/CVE-2026-67431.json"
  },
  "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.",
  "id": "CVE-2026-67431",
  "modified": "2026-07-31T03:34:09.327540398Z",
  "published": "2026-07-29T19:15:32.340Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/67xxx/CVE-2026-67431.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-5p9g-j988-pcwv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-67431"
    },
    {
      "type": "FIX",
      "url": "https://github.com/modelcontextprotocol/ruby-sdk/commit/35466605319a34e4c7808712ae9bb1ca1afb2356"
    }
  ],
  "schema_version": "1.8.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "MCP Ruby SDK: Ruby SSE Session Poisoning"
}