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Is Your Azure Cloud at Risk from the Newly Patched Bastion Authentication Bypass?
Microsoft fixed a dangerous security hole in Azure Bastion on November 21, 2025. This flaw, tracked as CVE-2025-49752, earned the worst possible security rating—a perfect 10.0 out of 10. Every Azure Bastion setup running before November 20, 2025, was at risk.
What Azure Bastion Does
Azure Bastion acts like a secure doorway to your cloud computers. It lets you connect to virtual machines through RDP and SSH without putting those machines directly on the internet. The service uses private addresses instead of public ones. You access everything through your web browser or a special app, with connections protected by TLS encryption.
The Security Problem
Hackers could steal login tokens and replay them to break into your systems. With one network request, attackers could jump straight to admin level and control any virtual machine connected through Bastion.
The flaw is especially dangerous because:
- Works from anywhere on the network
- Needs zero clicks from users
- Requires no special login first
- Bypasses normal security checks completely
Thankfully, Microsoft says nobody has used this weakness to attack real systems yet.
What You Should Do
Microsoft already patched the problem automatically. No action needed on your part. But smart teams should still check their logs for weird login attempts. Consider changing passwords for accounts that access Bastion, and turn on alerts for suspicious admin activity.