CVE-2026-59950

HIGHNVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 under NVD CVSS v3. EPSS exploit probability: 0.1%, 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
8.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.1Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
8.1
EG Score
8.1(medium)
EG Risk
37(Track)
EG Risk 37/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity81% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
5%
KEV
Not listed

Published

July 15, 2026

Last Modified

July 17, 2026

Advisory Details (4)

Auto-updated Jul 15, 2026
Patch 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/v1.28.1
github_commit

commit 777b8d06710c (modelcontextprotocol/python-sdk)

Fix landed in modelcontextprotocol/python-sdk commit 777b8d06710c — awaiting tagged release

https://github.com/modelcontextprotocol/python-sdk/commit/777b8d06710c140e3606b0d4598e2aa48546c266
github_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/2992
github 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-gjh5-988w

Vendor 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)
PackageVulnerable rangeFixed inDependents
mcp0.9.1 ... 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 13× in last 7d / 22× 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.

  1. 2026-07-26 11:29 UTCEG score recompute
  2. 2026-07-25 14:18 UTCEPSS rescore
  3. 2026-07-25 14:18 UTCEPSS rescore
  4. 2026-07-24 14:18 UTCEPSS rescore
  5. 2026-07-24 14:18 UTCEPSS rescore
  6. 2026-07-23 14:18 UTCEPSS rescore
  7. 2026-07-23 14:18 UTCEPSS rescore
  8. 2026-07-23 03:21 UTCEG score recompute
  9. 2026-07-22 14:08 UTCEPSS rescore
  10. 2026-07-22 14:08 UTCEPSS rescore
  11. 2026-07-21 15:25 UTCEPSS rescore
  12. 2026-07-21 15:25 UTCEPSS rescore
  13. 2026-07-20 17:08 UTCEPSS rescore
  14. 2026-07-19 14:31 UTCEPSS rescore
  15. 2026-07-19 02:37 UTCEG score recompute▲ 0.50
  16. 2026-07-19 02:29 UTCEPSS rescore
  17. 2026-07-18 10:04 UTCEPSS rescore
  18. 2026-07-17 20:00 UTCNVD updateCVSS v3 → 8.1
  19. 2026-07-17 13:37 UTCEG score recompute
  20. 2026-07-16 17:03 UTCEPSS rescore
  21. 2026-07-15 20:35 UTCEG score recompute
  22. 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 0% probability of exploitation in the next 30 days, which ranks it in the top 95.4% of all scored CVEs.
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

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