High severityNVD Advisory· Published Jul 15, 2026· Updated Jul 17, 2026
MCP Python SDK: WebSocket server transport does not support Host/Origin validation
CVE-2026-59950
Description
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.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
mcpPyPI | < 1.28.1 | 1.28.1 |
Affected products
4- Range: <1.28.1
- osv-coords3 versions
< 1.93.0-r0+ 2 more
- (no CPE)range: < 1.93.0-r0
- (no CPE)range: < 1.172.0-r1
- (no CPE)range: < 1.172.0-r1
Patches
Vulnerability mechanics
References
6- github.com/advisories/GHSA-vj7q-gjh5-988wghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-59950ghsaADVISORY
- github.com/modelcontextprotocol/python-sdk/commit/777b8d06710c140e3606b0d4598e2aa48546c266ghsax_refsource_MISCWEB
- github.com/modelcontextprotocol/python-sdk/pull/2992ghsax_refsource_MISCWEB
- github.com/modelcontextprotocol/python-sdk/releases/tag/v1.28.1ghsax_refsource_MISCWEB
- github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-vj7q-gjh5-988wghsax_refsource_CONFIRMWEB
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