CVE-2026-59950

modelcontextprotocol python-sdkVulnerabilityCVSS 7.6

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.

No public exploitation has been reported so far. No distribution fix is listed yet; apply vendor mitigations and monitor.

Recommended action: Track your distribution's security tracker and apply the fix as soon as it ships.

CVE-2026-59950 modelcontextprotocol python-sdk Vulnerability

Severity metrics

CVSS 4.0 : 7.6 HIGH · CVSS 3.1 : 8.1 HIGH

Attack vectorNetwork (remote)

Attack complexityLow

Attack requirementsPresent

Privileges requiredNone

User interactionPassive

Confidentiality impactHigh

Integrity impactHigh

Availability impactNone

Subsequent confidentialityNone

Subsequent integrityNone

Subsequent availabilityNone

Vector: AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Affected & fixed versions by distribution

Versions are the native distribution strings (backport-aware): RHEL/Debian/SUSE backport fixes, so compare with the distro version comparator (dpkg / rpm / vercmp), not the upstream version.

No affected package in the tracked watchlist yet (Debian, Ubuntu, Arch, SUSE, Red Hat...). Triage may still be pending.

Sources

Advisory NVD CVE.org

Published 2026-07-15 · updated 2026-07-25 · source: NVD