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CVE-2026-52869

7.1 · HIGH

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP).

Published Jul 15, 2026CWE-639EPSS 0.53%

Overview

CVE-2026-52869 is a high-severity vulnerability. It was published on July 15, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical description

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_manager.StreamableHTTPSessionManager route requests to existing sessions using only the session_id query parameter or Mcp-Session-Id header without verifying the authenticated principal that created the session, allowing a different bearer-token-authenticated client with a known session ID to inject JSON-RPC messages into that session. This issue is fixed in version 1.27.2.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/modelcontextprotocol/python-sdk/commit/1abcca2408a6b50e10ec601181f63f9978705c00GitHubgithub.com/modelcontextprotocol/python-sdk/commit/ce267b6fc515dc4efc1dc70b6975b16ff0feef0aGitHubgithub.com/modelcontextprotocol/python-sdk/pull/2690GitHubgithub.com/modelcontextprotocol/python-sdk/pull/2719GitHubgithub.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2GitHubgithub.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-jpw9-pfvf-9f58

How CyberStrike helps

Frequently asked questions

What is CVE-2026-52869?

CVE-2026-52869 is a high-severity vulnerability. It was published on July 15, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).

How severe is CVE-2026-52869?

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-52869?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-52869?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-52869 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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