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.
CVE-2026-59950
HIGHPre-NVD 7.67.6
EchelonGraph scoreLOW confidence
This high-severity CVE scores 7.6 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: cna:github_m
7.6
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: —CVSS: 7.6Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.6
- EG Score
- 7.6(low)
- EPSS
- —
- KEV
- Not listed
Published
July 15, 2026
Last Modified
July 15, 2026
Advisory Details (4)
Auto-updated Jul 15, 2026Patch available. Sources: github, github_pr, github_commit, github_release.
github_release Patch Available
v1.28.1
Patch available: modelcontextprotocol/python-sdk v1.28.1
https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.28.1github_commit
commit 777b8d06710c (modelcontextprotocol/python-sdk)
Fix landed in modelcontextprotocol/python-sdk commit 777b8d06710c — awaiting tagged release
https://github.com/modelcontextprotocol/python-sdk/commit/777b8d06710c140e3606b0d4598e2aa48546c266github_pr
[v1.x] Support TransportSecuritySettings in the WebSocket server transport
Fix merged in modelcontextprotocol/python-sdk PR #2992 on 2026-06-26 — awaiting tagged release
https://github.com/modelcontextprotocol/python-sdk/pull/2992github Patch Available
WebSocket server transport does not support Host/Origin validation · Advisory · modelcontextprotocol/python-sdk · GitHub
https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-vj7q-gjh5-988wWeakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 2× in last 7d / 2× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-15 20:35 UTCEG score recompute
- 2026-07-15 20:34 UTCMITRE cvelistV5first tracked
Frequently asked(4)
What is CVE-2026-59950?
CVE-2026-59950 is a high vulnerability published on July 15, 2026. 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…
When was CVE-2026-59950 disclosed?
CVE-2026-59950 was first published in the National Vulnerability Database on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-59950?
CVE-2026-59950 has a CVSS v3 base score of 7.6 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-59950?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-59950, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-59950
Is Your Infrastructure Affected by CVE-2026-59950?
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