PatchTheCVECVE-2025-66390: In Microsoft Azure API Management through 2025-10-17, when self-service signup (username/password Basic Authen
CVE-2025-66390 is a critical-severity flaw (CVSS 9.8) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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 Hos
Why this priority
- Critical severity
- CISA SSVC: public proof of concept
- CISA SSVC: automatable with total technical impact
- Remotely exploitable, no login, no user action
- On your watchlist
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.4% (top 62%) |
| CISA exploited list | No |
| Weakness | CWE-284 |
| Published | 2026-07-21 |
| Last modified | 2026-10-12 |
Last updated 2026-10-12 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Timeline
- Published CVE record published
- Updated Record last modified
Exact fixes by distribution
Public exploits and detection
Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2025-66390?
No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.
Is CVE-2025-66390 being exploited?
CVE-2025-66390 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2025-66390 affect?
CVE-2025-66390 affects affected software. Severity is critical (CVSS 9.8). 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 Ten
How urgent is CVE-2025-66390?
Priority 60/100. Critical severity; CISA SSVC: public proof of concept; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist