CVE-2025-53366

HIGHNVD 8.78.7—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.7 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 59% 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
8.7
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 6%CVSS: 8.7Exploit: NoneExposed: 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 version 1.9.4, a validation error in the MCP SDK can cause an unhandled exception when processing malformed requests, resulting in service unavailability (500 errors) until manually restarted. Impact may vary depending on the deployment conditions, and presence of infrastructure-level resilience measures. Version 1.9.4 contains a patch for the issue.

CVSS v3
8.7
EG Score
8.7(medium)
EG Risk
—
EPSS
92.2%
KEV
Not listed

Published

July 4, 2025

Last Modified

April 15, 2026

References (3)

Vendor Advisories for CVE-2025-53366(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 ... 1.9.3 (23 versions)1.9.4—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 40× 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.

Showing the most recent 100 of 115 total refreshes for this CVE.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-22 14:07 UTCEPSS rescore
  3. 2026-07-21 15:24 UTCEPSS rescore
  4. 2026-07-20 17:08 UTCEPSS rescore
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  12. 2026-07-15 01:59 UTCEPSS rescore
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  14. 2026-07-14 07:10 UTCOSV refresh
  15. 2026-07-13 22:29 UTCEPSS rescore
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  1. 2026-07-06 02:23 UTCEPSS rescore
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  3. 2026-07-05 02:30 UTCEPSS rescore
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  5. 2026-07-02 17:01 UTCEPSS rescore
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  7. 2026-06-30 23:22 UTCEPSS rescore
  8. 2026-06-28 04:55 UTCEPSS rescore
  9. 2026-06-27 03:08 UTCEPSS rescore
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  11. 2026-06-26 04:46 UTCOSV refresh
  12. 2026-06-25 13:49 UTCEPSS rescore
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  15. 2026-06-23 21:32 UTCEPSS rescore
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  21. 2026-06-19 19:25 UTCEPSS rescore
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  23. 2026-06-18 17:52 UTCEPSS rescore
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  26. 2026-06-16 17:52 UTCEPSS rescore
  27. 2026-06-16 17:52 UTCEPSS rescore
  28. 2026-06-15 17:48 UTCEPSS rescore
  29. 2026-06-14 23:17 UTCEPSS rescore
  30. 2026-06-13 23:00 UTCEPSS rescore
  31. 2026-06-12 23:11 UTCEPSS rescore
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  36. 2026-06-10 13:22 UTCEPSS rescore
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  38. 2026-06-08 16:01 UTCEG score recompute▲ 8.70
  39. 2026-06-08 14:16 UTCEPSS rescore
  40. 2026-06-08 14:16 UTCEPSS rescore
  41. 2026-06-07 15:24 UTCEPSS rescore
  42. 2026-06-07 15:24 UTCEPSS rescore
  43. 2026-06-06 13:47 UTCEPSS rescore
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  45. 2026-06-05 22:46 UTCEPSS rescore
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  47. 2026-06-05 06:10 UTCEPSS rescore
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  49. 2026-06-04 13:12 UTCEPSS rescore
  50. 2026-06-04 13:12 UTCEPSS rescore
  51. 2026-06-03 01:10 UTCOSV refresh
  52. 2026-06-02 20:12 UTCEPSS rescore
  53. 2026-06-02 20:12 UTCEPSS rescore
  54. 2026-06-01 13:51 UTCEPSS rescore
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  56. 2026-05-31 22:30 UTCEPSS rescore
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  72. 2026-05-26 07:18 UTCEPSS rescore
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  74. 2026-05-26 07:18 UTCEPSS rescore
  75. 2026-05-24 16:57 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2025-53366?
CVE-2025-53366 is a high vulnerability published on July 4, 2025. The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to version 1.9.4, a validation error in the MCP SDK can cause an unhandled exception when processing malformed requests, resulting in service unavailability (500 errors) until manually…
When was CVE-2025-53366 disclosed?
CVE-2025-53366 was first published in the National Vulnerability Database on July 4, 2025, with the most recent update on April 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-53366 actively exploited?
CVE-2025-53366 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 92.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2025-53366?
CVE-2025-53366 has a CVSS v3 base score of 8.7 (NVD).
How do I remediate CVE-2025-53366?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-53366, 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

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