Auth bypass in Modelcontextprotocol Python-sdk
CVE-2026-52869
The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to 1.27.2, the SSE and stateful Streamable HTTP transports mcp.server.sse.SseServerTransport and mcp.server.streamable_http_manag…
Vulnerability class: IDOR (Insecure Direct Object Reference)
CVSS v3 metric
CVSS v3 base score 7.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L.
Affected products
- Modelcontextprotocol Python-sdk — versions < 1.27.2
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_CONFIRM)
Frequently asked questions
- What is CVE-2026-52869?
- CVE-2026-52869 is a high-severity vulnerability in Modelcontextprotocol Python-sdk, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 7.1/10. Published 2026-07-15.
- How severe is CVE-2026-52869?
- High severity. CVSS v3 base score is 7.1 out of 10.