CVE-2025-66390
CRITICALIn 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…
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).
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2025-66390 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2025-66390 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2025-66390. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-66390 in your dependencies?
O3 detects CVE-2025-66390 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.