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
HIGHNVD 8.18.1—Trending — 3 sources updated this week
EchelonGraph scoreMEDIUM confidence
This high-severity CVE scores 8.1 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 95% of all CVEs by exploit prediction. 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: epss, nvd
8.1
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 8.1Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 8.1
- EG Score
- 8.1(medium)
- EPSS
- 4.8%
- KEV
- Not listed
Published
July 15, 2026
Last Modified
July 17, 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-gjh5-988wVendor Advisories for CVE-2026-59950(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| mcp | 0.9.1 ... 1.9.4 (57 versions) | 1.28.1 | — |
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 12× in last 7d / 14× 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.
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-21 15:25 UTCEPSS rescore
- 2026-07-21 15:25 UTCEPSS rescore
- 2026-07-20 17:08 UTCEPSS rescore
- 2026-07-19 14:31 UTCEPSS rescore
- 2026-07-19 02:37 UTCEG score recompute▲ 0.50
- 2026-07-19 02:29 UTCEPSS rescore
- 2026-07-18 10:04 UTCEPSS rescore
- 2026-07-17 20:00 UTCNVD updateCVSS v3 → 8.1
- 2026-07-17 13:37 UTCEG score recompute
- 2026-07-16 17:03 UTCEPSS rescore
- 2026-07-15 20:35 UTCEG score recompute
- 2026-07-15 20:34 UTCMITRE cvelistV5first tracked
Frequently asked(5)
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, with the most recent update on July 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-59950 actively exploited?
CVE-2026-59950 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 4.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-59950?
CVE-2026-59950 has a CVSS v3 base score of 8.1 (NVD).
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
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-59950
Is Your Infrastructure Affected by CVE-2026-59950?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.