In Microsoft Azure API Management through 2025-10-17, when self-service signup (username/password Basic Authentication) is enabled in Tenant A, an… (CVE-2025-66390)
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).
AI Analysis
Technical Summary
The issue in Microsoft Azure API Management involves the self-service signup API endpoint accepting cross-tenant requests based on the Host header, allowing an attacker to reuse the registration flow from Tenant A to Tenant B despite Tenant B having signup disabled at the UI level. The vendor's assessment clarifies that this behavior does not constitute a security boundary violation or exploitable tenant isolation vulnerability, but rather a configuration or state management concern.
Potential Impact
No direct security boundary is crossed, and tenant isolation is not compromised. The underlying API endpoint accepts cross-tenant requests, which may cause unexpected behavior in tenant signup configurations, but does not lead to unauthorized access or privilege escalation according to the vendor's evaluation.
Mitigation Recommendations
The vendor has determined this is a configuration/state issue rather than a product vulnerability affecting tenant isolation. No official patch or fix is indicated. Users should review tenant signup configurations and be aware of this behavior. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance.
In Microsoft Azure API Management through 2025-10-17, when self-service signup (username/password Basic Authentication) is enabled in Tenant A, an… (CVE-2025-66390)
Description
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 v3.1
Score 9.8critical
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The issue in Microsoft Azure API Management involves the self-service signup API endpoint accepting cross-tenant requests based on the Host header, allowing an attacker to reuse the registration flow from Tenant A to Tenant B despite Tenant B having signup disabled at the UI level. The vendor's assessment clarifies that this behavior does not constitute a security boundary violation or exploitable tenant isolation vulnerability, but rather a configuration or state management concern.
Potential Impact
No direct security boundary is crossed, and tenant isolation is not compromised. The underlying API endpoint accepts cross-tenant requests, which may cause unexpected behavior in tenant signup configurations, but does not lead to unauthorized access or privilege escalation according to the vendor's evaluation.
Mitigation Recommendations
The vendor has determined this is a configuration/state issue rather than a product vulnerability affecting tenant isolation. No official patch or fix is indicated. Users should review tenant signup configurations and be aware of this behavior. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-984h-wx22-r594
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2025-66390"]
- Ecosystems
- []
- Database Specific Severity
- null
- Cvss Version
- 3.1
Threat ID: 6a5fd1521010f89cc21c92ef
Added to database: 07/21/2026, 20:06:42 UTC
Last enriched: 07/22/2026, 17:41:40 UTC
Last updated: 08/27/2026, 10:52:06 UTC
Views: 29
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