High CVSS 8.1
CVE-2026-59950
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.
What this means
- Exposure
- Exploitable remotely over the network and without authentication — but only if a user opens booby-trapped content.
- Impact
- An attacker can read sensitive data and modify or destroy data.
- Weakness
- A request’s origin is not validated, letting a third-party site act on the user’s behalf.
- Likelihood
- Its EPSS score stays low: nothing points to imminent exploitation, which is no reason to leave it unpatched.
What to doFold into the next patch cycle.
Read automatically from the CVSS vector, the weakness type (CWE) and the EPSS score. The technical description above remains the one published by NIST.