modelcontextprotocol MCP up to 1.28.0 WebSocket Server input validation

Summaryinfo

A vulnerability was found in modelcontextprotocol MCP up to 1.28.0. It has been declared as critical. Impacted is an unknown function of the component WebSocket Server. Such manipulation leads to input validation. This vulnerability is documented as CVE-2026-59950. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in modelcontextprotocol MCP up to 1.28.0. Affected by this issue is some unknown processing of the component WebSocket Server. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality, integrity, and availability. CVE summarizes:

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to 1.28.1, the deprecated mcp.server.websocket.websocket_server transport accepted WebSocket handshakes without applying Host or Origin header validation, leaving no SDK-level way to restrict which origins could connect to applications that exposed that transport. This issue is fixed in version 1.28.1.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-59950 since 07/07/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. The technical details are unknown and an exploit is not available.

Upgrading to version 1.28.1 eliminates this vulnerability.

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Productinfo

Type

• Artificial Intelligence Software

Vendor

• modelcontextprotocol

Name

• MCP

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 1.22
• 1.23
• 1.24
• 1.25
• 1.26
• 1.27
• 1.28.0

CPE 2.3info

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• 🔒
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CPE 2.2info

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• 🔒
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