CVE-2025-66390

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-07-21. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
Trending — 3 sources updated this weekElevated
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: Elevated riskExposed: 0

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

In Microsoft Azure API Management through 2025-10-17, when self-service signup (username/password Basic Authentication) is enabled in Tenant A, an attacker can reuse the registration flow by changing the hostname or tenant identifier to Tenant B, even when Tenant B has signup disabled at the UI level. In other words, disabling signup in the UI does not disable the underlying API endpoint (which still accepts cross-tenant requests based on the Host header). NOTE: The supplier states that they evaluated the report and determined it did not cross a security boundary (i.e., the observed behavior was a configuration/state issue rather than an exploitable product vulnerability affecting tenant isolation). NOTE: The supplier evaluated this report and determined that it did not cross a security boundary (i.e., the observed behavior was a configuration/state issue rather than an exploitable product vulnerability affecting tenant isolation).

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
75(Attend)
EG Risk 75/100SSVC: Attend

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
Severity98% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
49%
KEV
Not listed

Published

July 21, 2026

Last Modified

July 23, 2026

Advisory Details (2)

Auto-updated Sep 12, 2026
Patch available. Sources: github.
generic

GitHub - bountyyfi/Azure-APIM-Cross-Tenant-Signup-Bypass: Security advisory: Azure APIM Developer Portal allows cross-tenant account registration by bypassing UI signup restrictions. Reported to MSRC twice - closed as "by design". · GitHub

https://github.com/bountyyfi/Azure-APIM-Cross-Tenant-Signup-Bypass
github Patch Available

Azure APIM Cross-Tenant Signup Bypass · Advisory · bountyyfi/Azure-APIM-Cross-Tenant-Signup-Bypass · GitHub

https://github.com/bountyyfi/Azure-APIM-Cross-Tenant-Signup-Bypass/security/advisories/GHSA-vcwf-73jp-r7mv

Vendor Advisories for CVE-2025-66390(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 27× in last 7d / 146× 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 349 total refreshes for this CVE.

  1. 2026-09-15 03:10 UTCEPSS rescore
  2. 2026-09-14 10:20 UTCGHSA enrichment
  3. 2026-09-14 06:13 UTCGHSA enrichment
  4. 2026-09-14 02:28 UTCGHSA enrichment
  5. 2026-09-13 22:42 UTCEG score recompute
  6. 2026-09-13 22:42 UTCGHSA enrichment
  7. 2026-09-13 16:46 UTCEPSS rescore
  8. 2026-09-13 15:58 UTCGHSA enrichment
  9. 2026-09-13 11:32 UTCGHSA enrichment
  10. 2026-09-13 07:02 UTCGHSA enrichment
  11. 2026-09-13 03:07 UTCGHSA enrichment
  12. 2026-09-12 19:21 UTCEG score recompute
  13. 2026-09-12 19:21 UTCGHSA enrichment
  14. 2026-09-12 15:00 UTCEPSS rescore
  15. 2026-09-12 13:35 UTCGHSA enrichment
  16. 2026-09-12 09:50 UTCGHSA enrichment
  17. 2026-09-12 05:49 UTCGHSA enrichment
  18. 2026-09-12 01:04 UTCGHSA enrichment
  19. 2026-09-11 18:31 UTCEG score recompute
  20. 2026-09-11 18:31 UTCGHSA enrichment
  21. 2026-09-11 14:52 UTCEPSS rescore
  22. 2026-09-11 09:36 UTCEPSS rescore
  23. 2026-09-11 09:16 UTCEG score recompute
  24. 2026-09-11 09:16 UTCGHSA enrichment
  25. 2026-09-10 09:34 UTCEPSS rescore
Show 75 more
  1. 2026-09-09 11:44 UTCEG score recompute
  2. 2026-09-09 11:44 UTCGHSA enrichment
  3. 2026-09-08 22:00 UTCEPSS rescore
  4. 2026-09-08 02:35 UTCGHSA enrichment
  5. 2026-09-07 22:46 UTCEG score recompute
  6. 2026-09-07 22:46 UTCGHSA enrichment
  7. 2026-09-07 16:00 UTCEPSS rescore
  8. 2026-09-06 15:51 UTCEG score recompute
  9. 2026-09-06 15:51 UTCGHSA enrichment
  10. 2026-09-06 13:47 UTCEPSS rescore
  11. 2026-09-06 11:21 UTCGHSA enrichment
  12. 2026-09-06 04:08 UTCGHSA enrichment
  13. 2026-09-05 23:36 UTCGHSA enrichment
  14. 2026-09-05 19:52 UTCEG score recompute
  15. 2026-09-05 19:51 UTCGHSA enrichment
  16. 2026-09-05 09:16 UTCEG score recompute
  17. 2026-09-05 09:16 UTCGHSA enrichment
  18. 2026-09-04 05:06 UTCEPSS rescore
  19. 2026-09-02 14:11 UTCEPSS rescore
  20. 2026-09-02 01:00 UTCEG score recompute
  21. 2026-09-02 01:00 UTCGHSA enrichment
  22. 2026-09-01 13:53 UTCEPSS rescore
  23. 2026-08-31 06:51 UTCGHSA enrichment
  24. 2026-08-31 02:41 UTCGHSA enrichment
  25. 2026-08-30 22:55 UTCEG score recompute
  26. 2026-08-30 22:55 UTCGHSA enrichment
  27. 2026-08-30 19:16 UTCEPSS rescore
  28. 2026-08-30 19:11 UTCGHSA enrichment
  29. 2026-08-30 15:26 UTCGHSA enrichment
  30. 2026-08-30 10:56 UTCGHSA enrichment
  31. 2026-08-30 06:12 UTCGHSA enrichment
  32. 2026-08-30 02:27 UTCEG score recompute
  33. 2026-08-30 02:27 UTCGHSA enrichment
  34. 2026-08-30 01:21 UTCEPSS rescore
  35. 2026-08-28 21:40 UTCEPSS rescore
  36. 2026-08-28 01:40 UTCGHSA enrichment
  37. 2026-08-27 21:19 UTCGHSA enrichment
  38. 2026-08-27 15:17 UTCEG score recompute
  39. 2026-08-27 15:17 UTCGHSA enrichment
  40. 2026-08-27 14:24 UTCEPSS rescore
  41. 2026-08-27 11:32 UTCGHSA enrichment
  42. 2026-08-27 05:12 UTCGHSA enrichment
  43. 2026-08-27 01:25 UTCGHSA enrichment
  44. 2026-08-26 21:41 UTCGHSA enrichment
  45. 2026-08-26 15:31 UTCEG score recompute
  46. 2026-08-26 15:31 UTCGHSA enrichment
  47. 2026-08-26 14:45 UTCEPSS rescore
  48. 2026-08-26 11:39 UTCGHSA enrichment
  49. 2026-08-26 07:18 UTCGHSA enrichment
  50. 2026-08-26 02:23 UTCGHSA enrichment
  51. 2026-08-25 22:38 UTCGHSA enrichment
  52. 2026-08-25 18:23 UTCEG score recompute
  53. 2026-08-25 18:23 UTCGHSA enrichment
  54. 2026-08-25 13:48 UTCEPSS rescore
  55. 2026-08-25 13:43 UTCGHSA enrichment
  56. 2026-08-25 09:58 UTCGHSA enrichment
  57. 2026-08-25 06:12 UTCGHSA enrichment
  58. 2026-08-25 02:24 UTCGHSA enrichment
  59. 2026-08-24 22:39 UTCGHSA enrichment
  60. 2026-08-24 18:55 UTCEG score recompute
  61. 2026-08-24 18:55 UTCGHSA enrichment
  62. 2026-08-24 14:16 UTCEPSS rescore
  63. 2026-08-24 12:59 UTCEG score recompute
  64. 2026-08-24 12:59 UTCGHSA enrichment
  65. 2026-08-24 09:14 UTCGHSA enrichment
  66. 2026-08-24 05:29 UTCGHSA enrichment
  67. 2026-08-24 01:42 UTCGHSA enrichment
  68. 2026-08-23 21:57 UTCGHSA enrichment
  69. 2026-08-23 18:12 UTCGHSA enrichment
  70. 2026-08-23 14:27 UTCGHSA enrichment
  71. 2026-08-23 10:42 UTCGHSA enrichment
  72. 2026-08-23 06:56 UTCGHSA enrichment
  73. 2026-08-23 03:11 UTCEG score recompute
  74. 2026-08-23 03:11 UTCGHSA enrichment
  75. 2026-08-23 00:18 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2025-66390?
CVE-2025-66390 is a critical vulnerability published on July 21, 2026. In Microsoft Azure API Management through 2025-10-17, when self-service signup (username/password Basic Authentication) is enabled in Tenant A, an attacker can reuse the registration flow by changing the hostname or tenant identifier to Tenant B, even when Tenant B has signup disabled at the UI…
When was CVE-2025-66390 disclosed?
CVE-2025-66390 was first published in the National Vulnerability Database on July 21, 2026, with the most recent update on July 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-66390 actively exploited?
CVE-2025-66390 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 51.2% of all scored CVEs.
What is the CVSS score of CVE-2025-66390?
CVE-2025-66390 has a CVSS v3.1 base score of 9.8 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2025-66390?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-66390, 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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