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.
- CVSS 4.0
- 7.6
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N - CVSS 3.1
- 8.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - EPSS
- 0.2% chance of exploitation in the next 30 days; higher than 13% of CVEs (scores of 2026-10-25)
- CWEs
- CWE-346, CWE-1385
- Published
- Modified
- Record from
- the NVD, synced
Affected
- lfprojects:mcp_python_sdk
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-vj7q-gjh5-988w | PyPI | mcp | <1.28.1 | 1.28.1 |
| PYSEC-2026-3483 | PyPI | mcp | <1.28.1 | 1.28.1 |
References
- https://github.com/modelcontextprotocol/python-sdk/commit/777b8d06710c140e3606b0d4598e2aa48546c266
- https://github.com/modelcontextprotocol/python-sdk/pull/2992
- https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.28.1
- https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-vj7q-gjh5-988w