CVE-2026-59950: The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP)

Q: How do I fix CVE-2026-59950?

mcp python sdk: upgrade to 1.28.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-59950 being exploited?

CVE-2026-59950 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-59950 affect?

CVE-2026-59950 affects mcp python sdk. Severity is high (CVSS 8.1). 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 O

Routine

HIGH 8.1UPGRADE

CVE-2026-59950 is a high-severity flaw (CVSS 8.1) affecting mcp python sdk. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 87%)
CISA exploited list	No
Weakness	CWE-346, CWE-1385
Published	2026-07-15
Last modified	2026-10-24

Publisher (CNA): GitHub, Inc. · Vendor: lfprojects

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-15 21:16 UTCPublished CVE record published
2026-10-24 21:10 UTCUpdated Record last modified

lfprojects mcp python sdk UPGRADE

Affected: < 1.28.1

Fixed in: 1.28.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy mcp-python-sdk || rpm -q mcp-python-sdk || mcp-python-sdk --version

2. UPGRADE to 1.28.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mcp-python-sdk

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mcp-python-sdk

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-59950?

mcp python sdk: upgrade to 1.28.1. Exact commands for each OS are on this page.

Is CVE-2026-59950 being exploited?

CVE-2026-59950 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-59950 affect?

CVE-2026-59950 affects mcp python sdk. Severity is high (CVSS 8.1). 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 O

How urgent is CVE-2026-59950?

Priority 32/100. High severity

Software pages

Python vulnerabilities · PyPI packages vulnerabilities

Related CVEs

CVE-2026-52869 HIGH 7.1 UPGRADE The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP)
CVE-2026-52870 HIGH 7.6 UPGRADE The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP)

References

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