A critical authentication bypass vulnerability in Microsoft Azure Bastion (CVE-2025-49752) allows remote attackers to escalate privileges to administrative levels without user interaction. With a CVSS score of 10.0, this flaw represents the highest severity classification and poses an immediate risk to organizations relying on Bastion for secure cloud access.
Why This Vulnerability Is Dangerous
Azure Bastion is designed to provide secure remote access to virtual machines without exposing them to the public internet. However, CVE-2025-49752 undermines this security model by enabling attackers to:
- Bypass authentication mechanisms
- Gain administrative access with a single network request
- Compromise all VMs connected to the Bastion host
Technical Details
According to Zeropath, the vulnerability stems from improper handling of authentication tokens within the Bastion service. Attackers can:
- Intercept valid authentication credentials
- Replay tokens to bypass security controls
- Assume administrative privileges remotely
Vulnerability Specifications
| Field | Details |
|---|---|
| CVE ID | CVE-2025-49752 |
| Type | Authentication Bypass (CWE-294) |
| CVSS Score | 10.0 (Critical) |
| Affected Product | Microsoft Azure Bastion (all versions prior to Nov 20, 2025) |
| Attack Vector | Network |
| Impact | Remote Privilege Escalation |
Exploitability
The critical aspect of CVE-2025-49752 is its network-based exploitability:
- No physical access required
- No prior authentication needed
- No user interaction necessary
An attacker anywhere on the network can compromise the entire Bastion infrastructure and all connected virtual machines.
Affected Deployments
All Azure Bastion deployments prior to November 20, 2025 are vulnerable. Microsoft has not released specific version numbers, suggesting all configurations using the service are impacted.
Mitigation Steps
Organizations should:
- Apply the latest security patches immediately
- Audit administrative access logs for unauthorized activity
- Review network segmentation and access controls
- Rotate authentication tokens and credentials
- Implement strict monitoring for replay attacks
Recurring Pattern in Azure Security
This flaw adds to a growing list of critical authentication and privilege escalation vulnerabilities discovered in Azure services throughout 2025, including:
- CVE-2025-54914
- CVE-2025-29827
Despite Microsoft’s Secure Future Initiative, recurring authentication issues continue to affect Azure infrastructure, emphasizing the need for robust third-party risk management and continuous monitoring.
Why This Matters
Azure Bastion is a cornerstone of secure cloud administration. A vulnerability of this magnitude can lead to:
- Full cloud environment compromise
- Data breaches
- Ransomware attacks
- Regulatory compliance failures
Immediate patching and proactive security measures are essential to prevent exploitation.
